Monte Carlo Model for Studying the Effects of Melanin Concentrations on Retina Light Absorption

We developed a Monte Carlo model to calculate light absorption in human and mouse retinas. The retina was modeled as a five-layer spherical structure. The effects of melanin concentrations in the retinal pigment epithelium (RPE) and choroid layer were studied. Variations of blood content in choroid were also considered in the simulation. Our simulation results indicated that light absorption in neural retina was at least 20% higher in albino subjects than in pigmented subjects under both photobleaching and dark-adapted conditions. It can be four times higher at optical wavelengths corresponding to minimal hemoglobin absorption. The elevated absorption at neural retina was attributed to the light backscattered from the choroid and sclera layers. This simulation model may provide useful information in studying light-induced retina damage

The activity of the endocannabinoid metabolising enzyme fatty acid amide hydrolase in subcutaneous adipocytes correlates with BMI in metabolically healthy humans

<p>Abstract</p> <p>Background</p> <p>The endocannabinoid system (ECS) is a ubiquitously expressed signalling system, with involvement in lipid metabolism and obesity. There are reported changes in obesity of blood concentrations of the endocannabinoids anandamide (AEA) and 2-arachidonoylglcyerol (2-AG), and of adipose tissue expression levels of the two key catabolic enzymes of the ECS, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Surprisingly, however, the activities of these enzymes have not been assayed in conditions of increasing adiposity. The aim of the current study was to investigate whether FAAH and MGL activities in human subcutaneous adipocytes are affected by body mass index (BMI), or other markers of adiposity and metabolism.</p> <p>Methods</p> <p>Subcutaneous abdominal mature adipocytes, fasting blood samples and anthropometric measurements were obtained from 28 metabolically healthy subjects representing a range of BMIs. FAAH and MGL activities were assayed in mature adipocytes using radiolabelled substrates. Serum glucose, insulin and adipokines were determined using ELISAs.</p> <p>Results</p> <p>MGL activity showed no relationship with BMI or other adiposity indices, metabolic markers (fasting serum insulin or glucose) or serum adipokine levels (adiponectin, leptin or resistin). In contrast, FAAH activity in subcutaneous adipocytes correlated positively with BMI and waist circumference, but not with skinfold thickness, metabolic markers or serum adipokine levels.</p> <p>Conclusions</p> <p>In this study, novel evidence is provided that FAAH activity in subcutaneous mature adipocytes increases with BMI, whereas MGL activity does not. These findings support the hypothesis that some components of the ECS are upregulated with increasing adiposity in humans, and that AEA and 2-AG may be regulated differently.</p

Preference of food saltiness and willingness to consume low-sodium content food in a Chinese population

OBJECTIVE: To compare the preference of food saltiness and the willingness to consume low‐sodium food among hypertensive older people, non‐hypertensive older people and non‐hypertensive young people in a Chinese population. DESIGN: A cross‐sectional study based on a quota sample. Three saltiness options (low‐sodium, medium-sodium and high‐sodium) of soup and bread were offered to each participant who rated the taste of each food on a 5‐point Likert scale. Then, the participants rated their willingness to consume the low-sodium content foods on a 5‐point Likert scale, given they were informed of the benefit of the low-sodium option. Generalised linear mixed model and multiple linear regression were used to analyse the data. SETTING: Elderly centres and community centres in Hong Kong. PARTICIPANTS: Sixty hypertensive older people, 49 non‐hypertensive older people and 60 non-hypertensive young people were recruited from June to August 2014. Measurements: The tastiness score and the willingness score were the primary outcome measures. The Chinese Health Literacy Scale for Low Salt Consumption – Hong Kong population (CHLSalt‐HK) was also assessed. RESULTS: The tastiness rating of the high‐sodium option of soup was significantly lower than the medium‐sodium option (p<0.001), but there was no significant difference between the low‐sodium and the medium‐sodium options (p=0.204). For bread, tastiness rating of the low‐sodium option and the high‐sodium option were significantly lower than the medium‐sodium option (p<0.001 for both options). The tastiness score of soup did not have significant difference across the groups (p=0.181), but that of bread from the hypertensive older adults (p=0.012) and the non‐hypertensive older adults (p=0.006) was significantly higher than the non‐hypertensive young adults. Higher willingness rating to consume the low‐sodium option was significantly (p<0.001) associated with higher tastiness rating of the low-sodium option of soup and bread, and weakly associated with higher health literacy of low salt intake (soup: p=0.041; bread: p=0.024). Hypertensive older adults tended to be more willing to consume the low‐sodium option than non‐hypertensive older adults for soup (p=0.009), there was insignificant difference between non‐hypertensive older adults and non‐hypertensive young adults (p=0.156). For bread, there was insignificant difference in willingness rating to consume low‐sodium option (p=0.375). CONCLUSION: Older people are at a higher risk of hypertension, reduction of salt intake is important for them to reduce their risk of cardiovascular diseases. There is room for reducing the sodium content of soup, while the sodium in bread should be reduced progressively. Improving the taste of low‐sodium food may help to promote reduction in dietary sodium intake.postprin

Factors controlling tropospheric O3, OH, NOx, and SO2 over the tropical Pacific during PEM-Tropics B

Observations over the tropical Pacific during the Pacific Exploratory Mission (PEM)-Tropics B experiment (March-April 1999) are analyzed. Concentrations of CO and long-lived nonmethane hydrocarbons in the region are significantly enhanced due to transport of pollutants from northern industrial continents. This pollutant import also enhances moderately O3 concentrations but not NOx concentrations. It therefore tends to depress OH concentrations over the tropical Pacific. These effects contrast to the large enhancements of O3 and NOx concentrations and the moderate increase of OH concentrations due to biomass burning outflow during the PEM-Tropics A experiment (September-October 1996). Observed CH3I concentrations, as in PEM-Tropics A, indicate that convective mass outflux in the middle and upper troposphere is largely independent of altitude over the tropical Pacific. Constraining a one-dimensiohal model with CH3I observations yields a 10-day timescale for convective turnover of the free troposphere, a factor of 2 faster than during PEM-Tropics A. Model simulated HO2, CH2O, H2O2, and CH3OOH concentrations are generally in agreement with observations. However, simulated OH concentrations are lower (∼25%) than observations above 6 km. Whereas models tend to overestimate previous field measurements, simulated HNO3 concentrations during PEM-Tropics B are too low (a factor of 2-4 below 6 km) compared to observations. Budget analyses indicate that chemical production of O3 accounts for only 50% of chemical loss; significant transport of O3 into the region appears to take place within the tropics. Convective transport of CH3OOH enhances the production of HOx and O3 in the upper troposphere, but this effect is offset by HOx loss due to the scavenging of H2O2. Convective transport and scavenging of reactive nitrogen species imply a necessary source of 0.4-1 Tg yr-1 of NOx in the free troposphere (above 4 km) over the tropics. A large fraction of the source could be from marine lightning. Oxidation of DMS transported by convection from the boundary layer could explain the observed free tropospheric SO2 concentrations over the tropical Pacific. This source of DMS due to convection, however, would imply in the model free tropospheric concentrations much higher than observed. The model overestimate cannot be reconciled using recent kinetics measurements of the DMS-OH adduct reaction at low pressures and temperatures and may reflect enhanced OH oxidation of DMS during convection. Copyright 2001 by the American Geophysical Union

Collective modes and correlations in one-component plasmas

The static and time-dependent potential and surface charge correlations in a plasma with a boundary are computed for different shapes of the boundary. The case of a spheroidal or spherical one-component plasma is studied in detail because experimental results are available for such systems. Also, since there is some knowlegde both experimental and theoretical about the electrostatic collective modes of these plasmas, the time-dependent correlations are computed using a method involving these modes.Comment: 20 pages, plain TeX, submitted to Phys. Rev.

The antidiabetic effects of a dry powder of dietary vegetable and fruit mixtures in diabetic db/db mice

We evaluated the antidiabetic effects of a mixed vegetable powder-formula I (MVP-FI), which is a dry powder mixture of over 65 kinds of vegetables and fruits, using the db/db type 2 diabetes mouse model. The db/db mice at 8-10 weeks of age were randomly divided into three groups: vehicle treatment, 1.575 g/kg MVP-FI treatment, and 3.15 g/kg MVP-FI treatment. During 12 days of treatment, we measured food intake and body weight changes, fasting blood glucose levels, and plasma lipid levels. Our results showed that the food intake and the body weight of MVP-FI-treated group were decreased gradually. Moreover, the fasting blood glucose level of the treated group was significantly dropped to a normal level comparable to that of the lean mice. Furthermore, we also found that the plasma triglyceride level in the treated group was dropped, whereas the high-density lipoprotein (HDL) level was increased and total cholesterol/HDL-cholesterol ratio was decreased. Taken together, these results suggest that the diabetic conditions of the db/db mice have been improved after 12 days treatment with MVP-FI. The antihyperglycemic and antiobese activities of the MVP-FI, as demonstrated in the present study, may have important clinical implications for improving the management of type 2 diabetic patients. © 2008 Yeung et al, publisher and licensee Dove Medical Press Ltd.published_or_final_versio

Bridging adaptive estimation and control with modern machine learning : a quorum sensing inspired algorithm for dynamic clustering

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 89-92).Quorum sensing is a decentralized biological process, by which a community of bacterial cells with no global awareness can coordinate their functional behaviors based only on local decision and cell-medium interaction. This thesis draws inspiration from quorum sensing to study the data clustering problem, in both the time-invariant and the time-varying cases. Borrowing ideas from both adaptive estimation and control, and modern machine learning, we propose an algorithm to estimate an "influence radius" for each cell that represents a single data, which is similar to a kernel tuning process in classical machine learning. Then we utilize the knowledge of local connectivity and neighborhood to cluster data into multiple colonies simultaneously. The entire process consists of two steps: first, the algorithm spots sparsely distributed "core cells" and determines for each cell its influence radius; then, associated "influence molecules" are secreted from the core cells and diffuse into the whole environment. The density distribution in the environment eventually determines the colony associated with each cell. We integrate the two steps into a dynamic process, which gives the algorithm flexibility for problems with time-varying data, such as dynamic grouping of swarms of robots. Finally, we demonstrate the algorithm on several applications, including benchmarks dataset testing, alleles information matching, and dynamic system grouping and identication. We hope our algorithm can shed light on the idea that biological inspiration can help design computational algorithms, as it provides a natural bond bridging adaptive estimation and control with modern machine learning.by Feng Tan.S.M

Families of p̳-adic Galois representations

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2011.Cataloged from PDF version of thesis. In title on title page, double underscored "p̳" appears as script.Includes bibliographical references (p. 121-124).In this thesis, I first generalize Kisin's theory of finite slope subspaces to arbitrary p-adic fields, and then apply it to the generic fibers of Galois deformation spaces. I study the finite slope deformation rings in details by computing the dimensions of their Zariski cotangent spaces via Galois cohomologies. It turns out that the Galois cohomologies tell us not only the formal smoothness of finite slope deformation rings, but also the behavior of the Sen operator near a generic de Rham representation. Applying these results to the finite slope subspace of two dimensional Galois representations of the absolute Galois group of a p-adic field, we are able to show that a generic (indecomposible) de Rham representation lies in the finite slope subspace. It follows from the construction of the finite slope subspace that the complete local ring of a point in the finite slope subspace is closely related to the finite slope deformation ring at the same point. As a consequence, we manage to show the flatness of the weight map near generic de Rham points, and accumulation and smoothness of generic de Rham points. In particular, we have a precise dimension formula for the finite slope subspace. Taking into account twists by characters, we define the nearly finite slope subspace, which is believed to serve as the local eigenvariety, as is suggested by Colmez's theory of trianguline representation. Following Gouv~a- Mazur and Kisin, we construct an infinite fern in the local Galois deformation space. Moreover, we define the global eigenvariety for GL2 over any number field, and give a lower bound of its dimension.by Fucheng Tan.Ph.D