Engineering vascularised tissues in vitro

Tissue engineering aims at replacing or regenerating tissues lost due to diseases or traumas (Langer and Vacanti, 1993). However, mimicking in vitro the physiological complexity of vascularized tissue is a major obstacle, which possibly contributes to impaired healing in vivo. In higher organisms, native features including the vascular network, the lymphatic networks and interstitial flow promote both mass transport and organ development. Attempts to mimic those features in engineered tissues will lead to more clinically relevant cell-based therapies. Aside from current strategies promoting angiogenesis from the host, an alternative concept termed prevascularization is emerging. It aims at creating a biological vasculature inside an engineered tissue prior to implantation. This vasculature can rapidly anastamose with the host and enhances tissue survival and differentiation. Interestingly, growing evidence supports a role of the vasculature in regulating pattern formation and tissue differentiation. Thus, prevascularized tissues also benefit from an intrinsic contribution of their vascular system to their development. From those early attempts are emerging a body of principles and strategies to grow and maintain, in vitro, those self-assembled biological vascular networks. This could lead to the generation of engineered tissues of more physiologically relevant complexity and improved regenerative potential

Proton Spin Content From Lattice QCD

We calculate the form factor of the quark energy momentum tensor and thereby extract the quark orbital angular momentum of the nucleon. The calculation is done on a quenched $16^3 \times 24$ lattice at $\beta = 6.0$ and with Wilson fermions at $\kappa$ = 0.148, 0.152, 0.154 and 0.155. We calculate the disconnected insertion stochastically which employs the $Z_2$ noise with an unbiased subtraction. This proves to be an efficient method of reduce the error from the noise. We find that the total quark contribution to the proton spin is $0.29 \pm 0.07$. From this we deduce that the quark orbital angular momentum is $0.17 \pm 0.08$ and predict the gluon spin to be $0.21 \pm 0.07$, i.e. about 40% of the proton spin is due to the glue.Comment: LATTICE99(Matrix Elements), 3 pages, 3 figure

Medical Oxygen Concentrators for Releasing Seed Dormancy

A new method is demonstrated for using concentrated oxygen (O2 gas) to release seed dormancy. Concentrated O2 gas in air is known to release seed dormancy in some seeds, including some foxtail (Setaria) species. New medical equipment makes O2 gas easier to work with than before, so laboratories working with dormant seeds can now use concentrated O2 gas as a seed treatment on a production basis. Use of medical O2 gas concentrators is simpler and safer than using O2 gas supplied by pressurized gas cylinders. Suitable medical O2 gas concentrators in new or used condition are readily available, operate on standard electrical current, and deliver O2 gas with low-pressure tubes and fittings. Resealable plastic bags are inflated with concentrated O2 gas and then sealed as seed treatment chambers. This use of concentrated O2 gas is confirmed to significantly increase the germination of dormant seeds of giant foxtail (Setaria faberi Herrm) and plains bristlegrass (S. macrostachya Kunth)

Global impact of COVID-19 on non-communicable disease management: descriptive analysis of access to FRAX fracture risk online tool for prevention of osteoporotic fractures

Summary The COVID-19 pandemic, and its management, is markedly impacting the management of osteoporosis as judged by access to online FRAX fracture risk assessments. Globally, access was 58% lower in April than in February 2020. Strategies to improve osteoporosis care, with greater use of fracture risk assessments, offer a partial solution. Introduction The COVID-19 pandemic is having a significant detrimental impact on the management of chronic diseases including osteoporosis. We have quantified the global impact by examining changes in the usage of online FRAX fracture risk assessments before and after the declaration of the pandemic (11 March 2020). Methods The study comprised a retrospective analysis using GoogleAnalytics data on daily sessions on the FRAX® website (www.sheffield.ac.uk/FRAX) from November 2019 to April 2020 (main analysis period February–April 2020), and the geographical source of that activity. Results Over February–April 2020, the FRAX website recorded 460,495 sessions from 184 countries, with 210,656 sessions in February alone. In March and April, the number of sessions fell by 23.1% and 58.3% respectively, a pattern not observed over the same period in 2019. There were smaller reductions in Asia than elsewhere, partly related to earlier and less-marked nadirs in some countries (China, Taiwan, Hong Kong, South Korea and Vietnam). In Europe, the majority of countries (24/31, 77.4%) reduced usage by at least 50% in April. Seven countries showed smaller reductions (range − 2.85 to − 44.1%) including Poland, Slovakia, Czech Republic, Germany, Norway, Sweden and Finland. There was no significant relationship between the reduction in FRAX usage and measures of disease burden such as COVID-attributed deaths per million of the population. Conclusion This study documents a marked global impact of the COVID-19 pandemic on the management of osteoporosis as reflected by FRAX online fracture risk assessments. The analysis suggests that impact may relate to the societal and healthcare measures taken to ameliorate the pandemic

Affine equivariant rank-weighted L-estimation of multivariate location

In the multivariate one-sample location model, we propose a class of flexible robust, affine-equivariant L-estimators of location, for distributions invoking affine-invariance of Mahalanobis distances of individual observations. An involved iteration process for their computation is numerically illustrated.Comment: 16 pages, 4 figures, 6 table

A surrogate FRAX model for the Kyrgyz Republic

Summary The hip fracture rates from Kazakhstan were used to create a surrogate FRAX® model for the Kyrgyz Republic. Introduction The International Society for Clinical Densitometry and International Osteoporosis Foundation recommend utilizing a surrogate FRAX model, based on the country-specific risk of death, and fracture data based on a country where fracture rates are considered to be representative of the index country. Objective This paper describes a surrogate FRAX model for the Kyrgyz Republic. Methods The FRAX model used the incidence of hip fracture from the neighbouring country of Kazakhstan and the death risk for the Kyrgyz Republic. Results Compared with the model for Kazakhstan, the surrogate model gave somewhat higher 10-year fracture probabilities for men between 60 and 80 years of age and lower probabilities for men above the age of 80. For women the probabilities were similar up to the age of 75–80 years and then lower. There were very close correlations in fracture probabilities between the surrogate and authentic models (1.00) so that the use of the Kyrgyz model had little impact on the rank order of risk. It was estimated that 2752 hip fractures arose in 2015 in individuals over the age of 50 years in the Kyrgyz Republic, with a predicted increase by 207% to 8435 in 2050. Conclusion The surrogate FRAX model for the Kyrgyz Republic provides the opportunity to determine fracture probability among the Kyrgyz population and help guide decisions about treatment

Epidemiology of osteoporotic fracture in Kazakhstan and development of a country specific FRAX model

Summary Retrospective and prospective population-based survey in a region of the Republic of Kazakhstan determined the incidence of fractures at the hip, proximal humerus and distal forearm. The hip fracture rates were used to create a FRAX® model to enhance fracture risk assessment in Kazakhstan. Objective This paper describes the epidemiology of osteoporotic fractures in the Republic of Kazakhstan that was used to develop a country specific FRAX® tool for fracture prediction. Methods We carried out a retrospective population-based survey in Taldykorgan in the Republic of Kazakhstan representing approximately 1% of the country’s population. Hip, forearm and humerus fractures were identified retrospectively in 2015 and 2016 from hospital registers and the trauma centre. Hip fractures were prospectively identified in 2017 from the same sources and additionally from primary care data. Age- and sex-specific incidence of hip fracture and national mortality rates were incorporated into a FRAX model for Kazakhstan. Fracture probabilities were compared with those from neighbouring countries having FRAX models. Results The difference in hip fracture incidence between the retrospective and prospective survey indicated that approximately 25% of hip fracture cases did not come to hospital attention. The incidence of hip fracture applied nationally suggested that the estimated number of hip fractures nationwide in persons over the age of 50 years for 2015 was 11,690 and is predicted to increase by 140% to 28,000 in 2050. Hip fracture incidence was a good predictor of forearm and humeral fractures in men but not in women. Conclusion The FRAX model should enhance accuracy of determining fracture probability among the Kazakh population and help guide decisions about treatment

Epidemiology of hip fractures in Bulgaria : development of a country-specific FRAX model

Summary A retrospective population-based survey was undertaken in a region of Bulgaria to determine the incidence of hip fracture. The estimated number of hip fractures nationwide for 2015 was 9322 and is predicted to increase to 11,398 in 2050. The hip fracture rates were used to create a FRAX model. Objective To describe the epidemiology of hip fractures in Bulgaria, which was then used to develop the country-specific fracture prediction FRAX® tool. Methods We carried out a retrospective population-based survey in Stara Zagora, Bulgaria, representing approximately 4.6% of the country’s population. We identified hip fractures occurring in 2015, 2016 and 2017 from hospital registers and primary care sources held by the regional health insurance agency. Age- and sex-specific incidence of hip fracture and national mortality rates were incorporated into a FRAX model for Bulgaria. Fracture probabilities were compared with those from neighbouring countries having FRAX models. Results The incidence of hip fracture applied nationally suggested that the estimated number of hip fractures nationwide in persons over the age of 50 years for 2015 was 9322 and is predicted to increase to 11,398 in 2050. FRAX-based probabilities were higher in Bulgaria than those in Serbia or Romania, lower than those in Turkey and similar to those in Greece. Conclusion The FRAX model should enhance accuracy of determining fracture probability among the Bulgarian population and help guide decisions about treatment

Computer-aided design of nano-filter construction using DNA self-assembly

Computer-aided design plays a fundamental role in both top-down and bottom-up nano-system fabrication. This paper presents a bottom-up nano-filter patterning process based on DNA self-assembly. In this study we designed a new method to construct fully designed nano-filters with the pores between 5 nm and 9 nm in diameter. Our calculations illustrated that by constructing such a nano-filter we would be able to separate many molecules

Residues and World-Sheet Instantons

We reconsider the question of which Calabi-Yau compactifications of the heterotic string are stable under world-sheet instanton corrections to the effective space-time superpotential. For instance, compactifications described by (0,2) linear sigma models are believed to be stable, suggesting a remarkable cancellation among the instanton effects in these theories. Here, we show that this cancellation follows directly from a residue theorem, whose proof relies only upon the right-moving world-sheet supersymmetries and suitable compactness properties of the (0,2) linear sigma model. Our residue theorem also extends to a new class of "half-linear" sigma models. Using these half-linear models, we show that heterotic compactifications on the quintic hypersurface in CP^4 for which the gauge bundle pulls back from a bundle on CP^4 are stable. Finally, we apply similar ideas to compute the superpotential contributions from families of membrane instantons in M-theory compactifications on manifolds of G_2 holonomy.Comment: 47 page