Structures and stabilities of H₂ adlayers on ionic crystal surfaces

Our Monte Carlo (MC) simulations investigate the possible formation of a series of structures, p (2{604}2)[arrow right] p (8{604}2)[arrow right] p (4{604}2)[arrow right] p (6{604}2) with coverages |=0.5, 0.625, 0.75 and 0.83 respectively, by H 2 molecules on the MgO(001) and LiF(001) surfaces. On H 2 /MgO(001) the sequence p (2{604}2)[arrow right] p (4{604}2)[arrow right] p (6{604}2) is possible and is stable up to 9 K, while on H 2 /LiF(001) the progression p (2{604}2)[arrow right] p (8{604}2)[arrow right] p (4{604}2) is found. These structures are consistent with recent Helium Atom Scattering (HAS) results in terms of coverage and thermal stability, but disagree in terms of symmetry. The HAS work found " c " type structures whereas the MC simulations (without quantum considerations) yield a " p " type structures. The p (2{604}2) structures contains two H 2 molecules per unit cell, with each molecule lying parallel to the plane of the surface ([straight theta] = 90{493}) directly above every other cationic site. The molecules adopt a "T" configuration with respect to their nearest neighbours. For the p (8{604}2), p (4{604}2) and p (6{604}2) structures, there are two kinds of adsorption sites: a parallel site, as in the case of p (2{604}2) structure, and a tilted site, where the H 2 molecules sit between cationic and anionic sites with the molecular axis directed towards the anionic site, with [straight theta] {598} 60{493}. To reconcile the results of the simulations and experiments, the quantum mechanical rotational motion of the adsorbed H 2 molecules was studied using perturbation theory. These calculations show that the adsorbed hydrogen molecules are azimuthally delocalized and hence these structures are indeed c -type. For the H 2 /NaCI(001) system, the MC simulations of the bi-layer system show that the formation of a second layer is possible, in which the molecules lie tilted ([straight theta] = 45{493}) at the top of the Cl - sites in a unit cell of p (2{604}1) symmetry. It also found the molecules in the bottom layer lie flat over the Na + sites and arranged in a unit cell of p (2{604}1) symmetry, where the molecules adopt a tee configuration along diagonals, and have the same orientation along the rows. In terms of thermal stability, the bottom layer is stable up to 12 K whereas the upper layer is orientationally disordered at T > 5 K and molecules desorb at T > 8 K. These predicted structures are in agreement with the experimental findings in terms of coverage and thermal stability but disagree in terms of symmetry since the PIRS-ATR and HAS experimental findings show a (1{604}1) structure. To solve this problem, the rotational motion of H 2 molecules has been studied using perturbation theory and it is found that quantum effects will azimuthally delocalize the orientation of the molecular axis of H 2 . Thus, those predicted structures become a (1{604}1) structure

GT2004-53122 TECHNICAL AND ECONOMICAL FEASIBILITY OF GAS TURBINE INLET COOLING USING EVAPORATIVE FOGGING SYSTEM IN TWO DIFFERENT LOCATIONS IN OMAN

ABSTRACT In this paper gas turbine power boost via inlet air evaporative fogging system is evaluated for power plants of 40 MW power output in two different locations in Sultanate of Oman. The cooling effect is quantified using evaporative cooling degree hour (ECDH) approach. The power output boost based on the month with the highest number of evaporative cooling degree hours reaches as high as 20% for both locations.. This is significant in view of the increased air conditioning load during summer months. It is found that the average net present value (NPV) of installing fogging system in Marmul is $4,622,018 and in Fahud is$6,182,496. It is also found that the purchase and installation costs are paid back within the first six months of system operation and for later years, annual revenue of over $500,000 is generated

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Crystal structure and density functional calculation of (E)-4-Hydroxy-3-methyl-N'- (thiophen-2-ylmethylene)-1,4-dihydroquinoxaline-2-carbohydrazide radical

The compound (E)-4-Hydroxy-3-methyl-N'-(thiophen-2-ylmethylene)-1,4-dihydroquinoxaline-2-carbohydrazide (C15H13N4O2S) is a stable free radical quinoxaline derivative. It was prepared by treatment of an acidified ethanolic solution of 3-methyl-2-(thiophen-2-ylmethylenehydrazinocarbonyl)quinoxaline-4-oxide with a solution of CuSO4.5H2O. The crystal structure shows that the molecule contains non-planar linking unit between quinoxaline and thiophene rings. Hydrogen bonding (N-H…O), π…π stacking and S…S intermolecular interactions may be effective in the stabilization of the crystal lattice. Density functional theory results agree well with X-ray experimental findings indicating that the free radical is indeed possible and that the stability of this compound might be attributed to the highly electron delocalization of the conjugation system over the whole compound along with the extra stabilization from the intramolecular interactions

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background: End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods: This study comprised an analysis of GlobalSurg-1 and-2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle-and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results: In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 percent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P &lt; 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P &lt; 0·001) in low-compared with middle-and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P &lt; 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P &lt; 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P &lt; 0·001). Conclusion: Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially