Determining a membrane's shear modulus, independent of its area-dilatation modulus, via capsule flow in a converging micro-capillary.

Determination of the elastic properties of the membrane of artificial capsules is essential for the better design of the various devices that are utilized in their engineering and biomedical applications. However this task is complicated owing to the combined effects of the shear and area-dilatation moduli on the capsule deformation. Based on computational investigation, we propose a new methodology to determine a membrane's shear modulus, independent of its area-dilatation modulus, by flowing strain-hardening capsules in a converging micro-capillary of comparable size under Stokes flow conditions, and comparing the experimental measurements of the capsule elongation overshooting with computational data. The capsule prestress, if any, can also be determined with the same methodology. The elongation overshooting is practically independent of the viscosity ratio for low and moderate viscosity ratios, and thus a wide range of capsule fluids can be employed. Our proposed experimental device can be readily produced via glass fabrication while owing to the continuous flow in the micro-capillary, the characterization of a large number of artificial capsules is possible.

A comparative study of salivary buffering capacity, flow rate, resting pH, and salivary Immunoglobulin A in children with rampant caries and caries-resistant children.

PURPOSE: This study was conducted to identify various factors in the development of rampant type of dental caries in South Kerala children, other than high sucrose intake and poor oral hygiene. This was done by comparing the salivary buffering capacity(BC), flow-rate(FR), resting pH and salivary immunoglobulin-A(s-IgA) levels in children who are caries resistant(CR) and who have rampant dental caries. MATERIALS AND METHODS: Two study groups, a rampant caries group(RC) with more than five active caries lesions in the early stages and a CR with no caries lesions were selected based on a specific criteria. Unstimulated whole mixed saliva was collected directly from the floor of the mouth for a period of 10 min and the FR was calculated. Resting pH of saliva was measured using color coded pH paper. BC was measured by calculating the amount of citric acid of pH2.5, required to lower the initial pH of saliva down to 3. s-IgA levels were also estimated by immunoturbidometric method after forming a precipitate of s-IgA with specific anti-IgA antibodies. RESULT: The salivary BC, FRs, pH and s-IgA levels were significantly lower in the RC group when compared to the CR group. CONCLUSION: This study showed that salivary BC, flow-rate, resting pH and levels of s-IgA in saliva are risk factors in the development of RC in children.

Deformation of an elastic capsule in a rectangular microfluidic channel.

In the present study we investigate computationally the deformation of an elastic capsule in a rectangular microfluidic channel and compare it with that of a droplet. In contrast to the bullet or parachute shape in a square or cylindrical channel where the capsule extends along the flow direction, in a rectangular channel the capsule extends mainly along the less-confined lateral direction of the channel cross-section (i.e. the channel width), obtaining a pebble-like shape. The different shape evolution in these two types of solid channels results from the different tension development on the capsule membrane required for interfacial stability. Furthermore, in asymmetric channel flows, capsules show a different deformation compared to droplets with constant surface tension (which extend mainly along the flow direction) and to vesicles which extend along the more-confined channel height. Therefore, our study highlights the different stability dynamics associated with these three types of interfaces. Our findings suggest that the erythrocyte deformation in asymmetric vessels (which is similar to that of capsules) results from the erythrocyte's inner spectrin skeleton rather than from its outer lipid bilayer.

Motion of an elastic capsule in a square microfluidic channel.

In the present study we investigate computationally the steady-state motion of an elastic capsule along the centerline of a square microfluidic channel and compare it with that in a cylindrical tube. In particular, we consider a slightly over-inflated elastic capsule made of a strain-hardening membrane with comparable shearing and area-dilatation resistance. Under the conditions studied in this paper (i.e., small, moderate, and large capsules at low and moderate flow rates), the capsule motion in a square channel is similar to and thus governed by the same scaling laws with the capsule motion in a cylindrical tube, even though in the channel the cross section in the upstream portion of large capsules is nonaxisymmetric (i.e., square-like with rounded corners). When the hydrodynamic forces on the membrane increase, the capsule develops a pointed downstream edge and a flattened rear (possibly with a negative curvature) so that the restoring tension forces are increased as also happens with droplets. Membrane tensions increase significantly with the capsule size while the area near the downstream tip is the most probable to rupture when a capsule flows in a microchannel. Because the membrane tensions increase with the interfacial deformation, a suitable Landau-Levich-Derjaguin-Bretherton analysis reveals that the lubrication film thickness h for large capsules depends on both the capillary number Ca and the capsule size a; our computations determine the latter dependence to be (in dimensionless form) h ~ a(-2) for the large capsules studied in this work. For small and moderate capsule sizes a, the capsule velocity Ux and additional pressure drop ΔP+ are governed by the same scaling laws as for high-viscosity droplets. The velocity and additional pressure drop of large thick capsules also follow the dynamics of high-viscosity droplets, and are affected by the lubrication film thickness. The motion of our large thick capsules is characterized by a Ux-U ~ h ~ a(-2) approach to the undisturbed average duct velocity and an additional pressure drop ΔP+ ~a(3)/h ~ a(5). By combining basic physical principles and geometric properties, we develop a theoretical analysis that explains the power laws we found for large capsules.

Is hysterectomy needed in ovarian cancer?

CONTEXT: Hysterectomy is an integral part of ovarian cancer surgery. The authors have evaluated the uterine involvement in ovarian cancer in this study. AIMS: Conventionally, removal of the uterus is considered an essential part of ovarian cancer surgery, but rationale for same in absence of its gross involvement is questionable. Aim of this study was to evaluate the microscopic involvement of uterus in ovarian cancer and whether there are any predictors of uterine involvement. SETTINGS AND DESIGN: Retrospective study. MATERIALS AND METHODS: The authors analyzed 128 patients of epithelial ovarian cancer (EOC) operated from 2004 January to 2008 June, who had not undergone hysterectomy previously. Data regarding their demographic, clinical, and pathological findings was collected and analyzed. STATISTICAL ANALYSIS USED: Chi-square test. RESULTS: Most of our patients (n=111) presented with stage III or above. Serous carcinoma was the most common histology encountered (86.7%). Uterus was grossly involved in only 19 patients and microscopic involvement was noted in 20 patients. Only one patient with absence of gross involvement had microscopic disease in the uterus. Involvement of the uterus was found to be independent of stage, type of tumor, laterality, and preoperative chemotherapy. The grade of tumor and gross uterine involvement were only factors that showed statistically significant correlation with microscopic uterine involvement. Only one patient had synchronous endometrial cancer. CONCLUSIONS: Uterine involvement in EOC is not common. Absence of gross uterine involvement reliably predicts absence of microscopic disease.

Optical deflection and sorting of microparticles in a near-field optical geometry.

Near-field optical micromanipulation permits new possibilities for controlled motion of trapped objects. In this work, we report an original geometry for optically deflecting and sorting micro-objects employing a total internal reflection microscope system. A small beam of laser light is delivered off-axis through a total internal reflection objective which creates an elongated evanescent illumination of light at a glass/water interface. Asymmetrical gradient and scattering forces from this light field are seen to deflect and sort polystyrene microparticles within a fluid flow. The speed of the deflected objects is dependent upon their intrinsic properties. We present a finite element method to calculate the optical forces for the evanescent waves. The numerical simulations are in good qualitative agreement with the experimental observations and elucidate features of the particle trajectory. In the size range of 1 microm to 5 microm in diameter, polystyrene spheres were found to be guided on average 2.9 +/- 0.7 faster than silica spheres. The velocity increased by 3.0 +/- 0.5 microms(-1) per microm increase in diameter for polystyrene spheres and 0.7 +/- 0.2 microms(-1) per microm for silica. We employ this size dependence for performing passive optical sorting within a microfluidic chip and is demonstrated in the accompanying video.

Phytochelatin synthesis and response of antioxidants during cadmium stress in Bacopa monnieri L.

The phytotoxicity imposed by cadmium (Cd) and its detoxifying responses of Bacopa monnieri L. have been investigated. Effect on biomass, photosynthetic pigments and protein level were evaluated as gross effect, while lipid peroxidation and electrolyte leakage reflected oxidative stress. Induction of phytochelatins and enzymatic and non-enzymatic antioxidants were monitored as plants primary and secondary metal detoxifying responses, respectively. Plants accumulated substantial amount of Cd in different plant parts (root, stem and leaf), the maximum being in roots (9240.11 microg g(-1) dw after 7 d at 100 microM). Cadmium induced oxidative stress, which was indicated by increase in lipid peroxidation and electrical conductivity with increase in metal concentration and exposure duration. Photosynthetic pigments showed progressive decline while protein showed slight increase at lower concentrations. Enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) showed stimulation except catalase (CAT, EC 1.11.1.6) which showed declining trend. Initially, an enhanced level of cysteine, glutathione and non-protein thiols was observed, which depleted with increase in exposure concentration and duration. Phytochelatins induced significantly at 10 microM Cd in roots and at 50 microM Cd in leaves. The phytochelatins decreased in roots at 50 microM Cd, which may be correlated with reduced level of GSH, probably due to reduced GR activity, which exerted increased oxidative stress as also evident by the phenotypic changes in the plant like browning of roots and slight yellowing of leaves. Thus, besides synthesis of phytochelatins, availability of GSH and concerted activity of GR seem to play a central role for Bacopa plants to combat oxidative stress caused by metal and to detoxify it. Plants ability to accumulate and tolerate high amount of Cd through enhanced level of PCs and various antioxidants suggest it to be a suitable candidate for phytoremediation.

Dental caries and associated factors in 12-year-old schoolchildren in Thiruvananthapuram, Kerala, India.

OBJECTIVES: The aims of the present study were to describe the dental health status of 12-year-old schoolchildren in Thiruvananthapuram, Kerala, India, and to identify sociodemographic factors, oral health behaviours, attitudes and knowledge related to dental caries experience. METHODS: The study took the form of a cross-sectional survey of 838 children in upper primary schools. A two-stage cluster sampling technique was used. Dental caries was measured using World Health Organization criteria. Sociodemographic factors, oral health behaviours, attitudes and knowledge were assessed by a self-administered questionnaire. RESULTS: The prevalence of dental caries in the permanent dentition was 27%. The mean number of decayed, missing and filled teeth was 0.5 (SD=0.9). The decayed component (D) constituted 91% of the total number of decayed, missing and filled teeth (DMFT). Multiple logistic regression analysis showed that children had a higher risk of having dental caries if they lived in urban area [OR=1.5, 95% confidence interval (CI)=1.1-2.1], had visited a dentist (OR=1.6, 95% CI=1.2-2.2), did not use a toothbrush (OR=1.9, 95% CI=1.2-2.9), consumed sweets (OR=1.4, 95% CI=1.0-1.9) or performed poorly in school (OR=1.7, 95% CI=1.0-2.3). CONCLUSIONS: The prevalence of caries in this sample of 12-year-old schoolchildren was low compared to that in other developing countries. The present study indicated that urban living conditions were associated with more dental caries. Since urbanization is rapid in India, oral health promotion at the present time would be valuable to prevent increased caries prevalence.

Incontinentia pigmentii acromians with seizure disorder: a case report.

Incontinentia pigmentii acromians (IPA) is a bizarre, irregularly shaped leukoderma of the trunk and extremities, characterized by marble cake-like whorls or streaks of hypopigmentation whose distribution can be unilateral or bilateral. Mode of inheritance is most consistent with an autosomal dominant type and in majority of the cases, one or more anomalies are present involving dermatological, dental and ocular disorders. A case of a female child, aged 2 1/2 yrs, referred from Pediatric neurology department, Medical College, Trivandrum with Incontinentia pigmentii acromians and seizure disorder is reported. Hamartomatous dental cusps and single maxillary central incisors have been associated with Incontinentia pigmentii acromians. A case of Incontinentia pigmentii acromians with hypoplastic teeth and tongue abnormalities is presented.

Caries prevalence and its relation to socio-economic status and oral hygiene practices in 600 pre-school children of Kerala-India.

This Study was undertaken to determine the caries status of pre-school children in Ulloor Panchayat of Trivandrum, Kerala and to determine the relation if any, between their caries and socio-economic status and oral practices. 200 children each from the low, middle arid higher socio-economic group were visually examined for caries by the same examiner in natural daylight. Caries was recorded according to the WHO criteria. Information regarding the childrens' oral hygiene practices were obtained through structured questionnaires to the care takers of the children. Computer analysis of the data collected showed that 43% of the study sample were caries free. Socio-economic level was found to have a negative association with caries status. The mode of tooth brushing was found to be significantly related to caries severity while the frequency of tooth brushing was found to have no association with caries prevalence and severity.

Salivary calculus: an insight into its pathogenesis--a case report of parotid sialolith in a 9 year old child.

The occurrence of sialolithiasis in children is uncommon, while parotid sialoliths are rare. A case of parotid sialolith in a 9 year old child is reported.

Comparison of sealing ability of three different root canal sealers--an in vitro study.

The main objective of endodontic therapy is complete obturation of the root canal system after it has been adequately prepared and sterilised. A wide variety of root canal sealers are available for obturation of the root canal system. A number of different invitro methods have been used to evaluate the sealing ability of endodontic filling materials. By combining one or two tests it may be possible to obtain information about sealing ability of the test material. Therefore, the present invitro study compared the sealing ability of three different root canal sealers, namely Sealapex, AH-26 and ZnOE by two different methods, bacterial leakage and dye penetration. The results showed that AH-26 has the maximum sealing ability followed by Sealapex and ZnOE.

Doomed angels--a case report.

A three year old female child was brought to the Department of Pedodontics, Dental College, Thiruvananthapuram with a greyish white papillomatous lesion involving a large area on the buccal mucosa. VDRL was positive for the little girl as well as her father and was positive in low concentrations for her one-month-old sister as well as her mother.

Effect of 4-META adhesive on bond strength and marginal seal of amalgam restorations and repairs--an in vitro study.

Amalgam remains unchallenged as a posterior restorative material. But its inability to bond to the teeth leads to some amount of microleakage at the restoration-tooth interface with associated problems such as post operative sensitivity, pulpal complications etc. Also a broken amalgam restoration requires replacement which will further weaken the tooth structure. Recently, 4-META has been introduced which can graft amalgam and composite to enamel, dentin and old amalgam restorations. In this study, the bonding and marginal sealing abilities of 4-META was assessed both at the tooth-amalgam interface and old amalgam fresh amalgam interface.

Surface treatment of enamel with laser--a potential alternative for acid etching--an in vitro study.

An in-vitro study was carried out on 80 human premolars to study the use of Nd:YAG laser as a potential alternative for acid etching in the surface treatment of enamel prior to sealant application. The determination of bond strength using Universal Testing Machine, Model 1011 and marginal leakage using the spectrophotometric dye recovery method showed no statistically significant difference between the groups with laser and acid surface treatments. But, there was a significantly lower bond strength and increased dye penetration in the group with no surface treatment. Scanning electron microscopic study of the interface between sealant and enamel surface of the acid and laser treated specimens was also carried out.