An open question in the metal hydride community is whether there are simple, physics-based design rules that dictate the thermodynamic properties of these materials across the variety of structures ...and chemistry they can exhibit. While black box machine learning-based algorithms can predict these properties with some success, they do not directly provide the basis on which these predictions are made, therefore complicating the a priori design of novel materials exhibiting a desired property value. In this work we demonstrate how feature importance, as identified by a gradient boosting tree regressor, uncovers the strong dependence of the metal hydride equilibrium H2 pressure on a volume-based descriptor that can be computed from just the elemental composition of the intermetallic alloy. Elucidation of this simple structure–property relationship is valid across a range of compositions, metal substitutions, and structural classes exhibited by intermetallic hydrides. This permits rational targeting of novel intermetallics for high-pressure hydrogen storage (low-stability hydrides) by their descriptor values, and we predict a known intermetallic to form a low-stability hydride (as confirmed by density functional theory calculations) that has not yet been experimentally investigated.
This study numerically investigates the performance of the melting process for a PCM based heat storage system under the effect of different variables in a vertical container with a copper metal ...foam. Different cases were studied and compared including the effects of variable porosities and pore densities, non-equilibrium porous medium model, a multiple-segment metal foam case and different heater locations in the system on the liquid fraction and temperature as presented by contour plots and diagrams. The results show high performance for the copper foam-PCM unit compared with on its own PCM, for reducing the melting time by almost 85%. By changing the location of constant temperature heater from the bottom to the side and top surface, the melting time decreases by 70.5% and 4.7%, respectively. By using a multiple-segment porous system, the melting time reduces by 3.5% compared with the case of uniform porosity. Furthermore, the more accurate non-equilibrium numerical model shows a 7.4% difference in the melting time compared with the equilibrium model. This study optimises the design to improve practical application performance and to reduce waste energy.
•Studying numerically the performance of the melting process for a PCM.•Porous-PCM composite reduces the melting time by 85% compared with on its own PCM.•The location of the heater has a great influence on the melting time.•Multiple-segment porous system shows better performance than the uniform porosity.•Non-equilibrium numerical model is more accurate than the equilibrium model.
Despite the benefits of buyer and seller collaboration and hence relationships extolled in extensive studies, issues of relationship power inhibit implementation of collaborative and relational ...approaches, particularly in some parts of the retail sector. Further, most research regards buyer–supplier collaboration and relations as dyadic or focal relationships, or perhaps in a network context, and typically investigates buyer–supplier collaboration and relations from a power-dependency perspective; and within vertical supply integration. Little attention has been given to the potential role of supply chain intermediaries, such as logistics service providers, in objectively and independently determining and managing the course of buyer–supplier collaboration and relations in a business-to-business context. This article appraises the potential role of buyer–supplier collaboration and relations and their relevant opportunities in the power-laden, contentious environment of the retail grocery sector. With an interdisciplinary approach, drawn from supply management, relationship management, and logistics and supply chain management, this article emphasises the importance of horizontal collaboration using fourth-party logistics structures as horizontal intermediary conduits, who act independently between retailers and suppliers to facilitate collaborative and relational activity.
•We emphasise the role of intermediaries in buyer–seller collaboration and relationship management.•Under-explored horizontal supply channels are explored in the form of Logistics Service Providers (LSPs).•Fourth-party Logistics (4PL) arrangements are proposed in an independent role to moderate buyer-seller collaboration.
Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of ...metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s 1 for use in emergency or backup power units, i. e. for stationary applications.
With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus.
In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized.
In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles.
In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications.
•Latest developments in the application of hydride technology.•Investigations on both stationary and mobile applications.•Special attention to metal hydride compressors.•Heat storage and H2 compression especially noted in the Outlook.
Despite recent advances in analytical and computational chemistry, lipid identification remains a significant challenge in lipidomics. Ion-mobility spectrometry provides an accurate measure of the ...molecules’ rotationally averaged collision cross-section (CCS) in the gas phase and is thus related to ionic shape. Here, we investigate the use of CCS as a highly specific molecular descriptor for identifying lipids in biological samples. Using traveling wave ion mobility mass spectrometry (MS), we measured the CCS values of over 200 lipids within multiple chemical classes. CCS values derived from ion mobility were not affected by instrument settings or chromatographic conditions, and they were highly reproducible on instruments located in independent laboratories (interlaboratory RSD < 3% for 98% of molecules). CCS values were used as additional molecular descriptors to identify brain lipids using a variety of traditional lipidomic approaches. The addition of CCS improved the reproducibility of analysis in a liquid chromatography-MS workflow and maximized the separation of isobaric species and the signal-to-noise ratio in direct-MS analyses (e.g., “shotgun” lipidomics and MS imaging). These results indicate that adding CCS to databases and lipidomics workflows increases the specificity and selectivity of analysis, thus improving the confidence in lipid identification compared to traditional analytical approaches. The CCS/accurate-mass database described here is made publicly available.
There is a need to understand antecedents to US teens’ use of information and communication technology (ICT). Research on the “digital divide” for access to ICT reports conflicting findings based on ...gender and demographic factors of parent income and education. This study expanded the “tool‐will‐skill” framework to examine how demographic factors, access to ICT tools, teen will factors and social networking skill explain variation in Internet use among US teens. The study analyzed national data from Pew Research Center’s survey of 1,060 US teens. Principal component analysis (PCA) identified six latent variables for teen will. A pre‐diagram depicts a conceptual framework and causal assumption of relationships between demographic factors, tool factors (ie, Internet access, smartphone access and tablet access), will factors (from PCA) and skill factors (Facebook, Instagram, Snapchat and Twitter). Multiple linear path analysis was conducted, and results reported. Recommendations are suggested for instructional practice, educational policy and future research.
Several factors are associated with increased hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT), but no reliable risk score has been established to determine the individual ...risk for HCC recurrence.
We aimed to develop and validate a Risk Estimation of Tumor Recurrence After Transplant (RETREAT) score for patients with HCC meeting Milan criteria by imaging.
Predictors of recurrence were tested in a development cohort of 721 patients who underwent LT between 2002 and 2012 at 3 academic transplant centers (University of California-San Francisco; Mayo Clinic, Rochester; and Mayo Clinic, Jacksonville) to create the RETREAT score. This was subsequently validated in a cohort of 341 patients also meeting Milan criteria by imaging who underwent LT at the University of Toronto transplant center using the C concordance statistic and net reclassification index.
Characteristics associated with post-LT HCC recurrence.
A total of 1061 patients participated in the study; 77.8% (825) were men, and the median (IQR) age was 58.2 (53.3-63.9) years in the development cohort and 56.4 (51.7-61.0) years in the validation cohort (P < .001). In the development cohort of 721 patients (542 men), median α-fetoprotein (AFP) level at the time of LT was 8.3 ng/mL; 9.4% had microvascular invasion (n = 68), and 22.1% were beyond Milan criteria on explant (n = 159) owing to understaging by pretransplantation imaging. Cumulative probabilities of HCC recurrence at 1 and 5 years were 5.7% and 12.8%, respectively. On multivariable Cox proportional hazards regression, 3 variables were independently associated with HCC recurrence: microvascular invasion, AFP at time of LT, and the sum of the largest viable tumor diameter and number of viable tumors on explant. The RETREAT score was created using these 3 variables, with scores ranging from 0 to 5 or higher that were highly predictive of HCC recurrence (C statistic, 0.77). RETREAT was able to stratify 5-year post-LT recurrence risk ranging from less than 3% with a score of 0 to greater than 75% with a score of 5 or higher. The validation cohort (n = 340; 283 men) had significantly higher microvascular invasion (23.8% n = 81, P < .001), explant beyond Milan criteria (37.3% n = 159, P < .001), and HCC recurrence at 5 years (17.9% n = 159, P = .03). RETREAT showed good model discrimination (C statistic, 0.82; 95% CI, 0.77-0.86) and superior recurrence risk classification compared with explant Milan criteria (net reclassification index, 0.40; P = .001) in the validation cohort.
We have developed and validated a simple and novel prognostic score that may improve post-LT HCC surveillance strategies and help identify patients who may benefit from future adjuvant therapies.
PurposeAccess to food through retail supply chain distribution can vary significantly among the urban poor and leads to household food insecurity. The paper explores this sustainable supply chain ...phenomenon through a field study among South Africa's urban poor.Design/methodology/approachUrban metabolic flows is the theoretical basis in the context of supply chain management (SCM). The field study comprised 59 semi-structured interviews in one South African township. Data were recorded, transcribed and translated, and coded using NVivo 12 to provide an inventory of eight themes categorized and patterned from the analysis.FindingsFindings indicate societal factors play a significant role affecting food distribution, access and security from a spatial perspective of retail outlet locations and a nutritional standpoint regarding quality and quantity of food.Research limitations/implicationsThe study is exploratory in one township, and while rigorously conducted, the generalizability of findings is limited to this context.Practical implicationsThe study practically contributes by providing guidance for food retailers and policymakers to include nutritional guidelines in their distribution planning, as well as the dynamics of diverse neighbourhoods that exist in modern urban contexts.Social implicationsNew forms of retail food distribution can provide better security and access to food for the urban poor, contributing to Sustainable Development Goals (SDGs) 2 Zero Hunger and 11 Liveable Cities.Originality/valueThe study is interdisciplinary and contributes by linking UN SDGs and SCM through urban metabolic flows from development studies as an overarching framework to enable analysis of relationships between physical, social and economic factors in the urban environment.
The selection of liver transplant candidates with hepatocellular carcinoma (HCC) relies mostly on tumor size and number. Instead of relying on these factors, we used poor tumor differentiation and ...cancer‐related symptoms to exclude patients likely to have advanced HCC with aggressive biology. We initially reported similar 5‐year survival for patients whose tumors exceeded (M+ group) and were within (M group) the Milan criteria. Herein, we validate our original data with a new prospective cohort and report the long‐term follow‐up (10‐years) using an intention‐to‐treat analysis. The previously published study (cohort 1) included 362 listed (294 transplanted) patients from January 1996 to August 2008. The validation cohort (cohort 2) includes 243 listed (105 M+ group, 76 beyond University of California San Francisco criteria; 210 transplanted) patients from September 2008 to December 2012. Median follow‐up from listing was 59.7 (26.8‐103) months. For the validation cohort 2, the actuarial survival from transplant for the M+ group was similar to that of the M group at 1 year, 3 years, and 5 years: 94%, 76%, and 69% versus 95%, 82%, and 78% (P = 0.3). For the combined cohorts 1 and 2, there were no significant differences in the 10‐year actuarial survival from transplant between groups. On an intention‐to‐treat basis, the dropout rate was higher in the M+ group and the 5‐year and 10‐year survival rates from listing were decreased in the M+ group. An alpha‐fetoprotein level >500 ng/mL predicted poorer outcomes for both the M and M+ groups. Conclusion: Tumor differentiation and cancer‐related symptoms of HCC can be used to select patients with advanced HCC who are appropriate candidates for liver transplantation; alpha‐fetoprotein level limitations should be incorporated in the listing criteria for patients within or beyond the Milan criteria. (Hepatology 2016;64:2077‐2088)
The influence of nitrogen doping on the hydrogen uptake and storage capacity of high surface area carbon materials is presented in this report. To generate suitable study materials, we have exploited ...the relationship between synthesis conditions and textural properties of zeolite-templated carbons to generate a range of high surface area carbons with similar pore size distribution but which are either N-doped or N-free. For N-doped carbons, the nitrogen content was kept within a narrow range of between 4.7 and 7.7 wt %. The carbon materials, irrespective of whether they were doped or not, exhibited high surface area (1900−3700 m2/g) and pore volume (0.99 and 1.88 cm3/g), a micropore surface area of 1500−2800 m2/g, and a micropore volume of 0.65−1.24 cm3/g. The hydrogen uptake varied between 4.1 and 6.9 wt %. We present experimental data that indicates that the effect of N-doping on hydrogen uptake is only apparent when related to the surface area and pore volume associated with micropores rather than total porosity. Furthermore, by considering the isosteric heat of hydrogen adsorption and excess hydrogen uptake on N-free or N-doped carbons, it is shown that N-doping can be beneficial at lower coverage (low hydrogen uptake) but is detrimental at higher coverage (higher hydrogen uptake). The findings are consistent with previous theoretical predictions on the effect of N-doping of carbon on hydrogen uptake. The findings, therefore, add new insights that are useful for the development of carbon materials with enhanced hydrogen storage capacity.
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