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Critically ill COVID-19 patients have a high reported incidence of thromboembolic complications and the optimal dose of thromboprophylaxis is not yet determined. The aim of this study was to investigate if 90-day mortality differed between patients treated with intermediate- or high-dose thromboprophylaxis.In this retrospective study, all critically ill COVID-19 patients admitted to intensive care from March 6th until July 15th, 2020, were eligible. Patients were categorized into groups according to daily dose of thromboprophylaxis. Dosing was based on local standardized recommendations, not on degree of critical illness or risk of thrombosis. Cox proportional hazards regression was used to estimate hazard ratios of death within 90 days from ICU admission. Multivariable models were adjusted for sex, age, body-mass index, Simplified Acute Physiology Score III, invasive respiratory support, glucocorticoids, and dosing strategy of thromboprophylaxis.A total of 165 patients were included; 92 intermediate- and 73 high-dose thromboprophylaxis. Baseline characteristics did not differ between groups. The 90-day mortality was 19.6% in patients with intermediate-dose and 19.2% in patients with high-dose thromboprophylaxis. Multivariable hazard ratio of death within 90 days was 0.74 (95% CI, 0.36-1.53) for the high-dose group compared to intermediate-dose group. Multivariable hazard ratio for thromboembolic events and bleedings within 28 days was 0.93 (95% CI 0.37-2.29) and 0.84 (95% CI 0.28-2.54) for high versus intermediate dose, respectively.A difference in 90-day mortality between intermediate- and high-dose thromboprophylaxis could neither be confirmed nor rejected due to a small sample size.

Appendicitis is the most common acute abdominal complication during pregnancy. If appendix perforation occurs there is an increasing risk of preterm delivery and other pregnancy complications.To assess the outcome of pregnancy after appendectomy, the mode of surgery used, appendectomy rates, and complications.A prospective cohort study of pregnant women with, or without, appendectomy at South Stockholm General Hospital, December 2015 to February 2021 in a setting where pregnant women are prioritized for surgery and laparoscopic surgery was standard of care in first half of pregnancy. Data on preoperative imaging, surgical method, intraoperative findings, microscopic findings, hospital stay, pregnancy, and 30-day complications were prospectively recorded in a local appendectomy register. A non-pregnant control group was gathered comprising women of fertile age in the same study interval.During the study period 50 pregnant women, of whom 44 gave birth, underwent appendectomy of 38 199 women giving birth. There were no differences between women with or without appendectomy in proportion of preterm delivery (4.5% vs. 5.6%), small-for-gestational age (2.3% vs. 6.2%), or Cesarean delivery (18.2% vs. 20.4%). The rate of appendix perforation was 19% in non-pregnant control group compared to 12% among pregnancy. There was no case of perforated appendix in the second half of pregnancy. However, women with gestational age20 weeks more frequently had an unaffected appendix compared to those operated ≤ 20 gestational weeks (4/11 vs. 2/39,Routine laparoscopic surgery and time priority for pregnant surgery is associated with a low risk of perforation, preterm birth and other complications. However, a low threshold for surgery may increase the risk of a negative exploration.

It is unknown whether the COVID-19 pandemic has had an impact on emergency surgical care in Sweden. This study aimed to compare frequency, treatment strategies, severity, and complication rate of appendicitis during the initial phase of the COVID-19 pandemic with those of previous years.In this single-center study, we identified all patients admitted with appendicitis between March 16 and June 16, 2020, at the Stockholm South General Hospital, and compared these with patients hospitalized with appendicitis during the same calendar period the three previous years. We used multivariate logistic regression to calculate Odds Ratios (OR) with 95% confidence intervals as measurement of the association between appendicitis treatment and perforation rate during the COVID-19 period compared to the nonCOVID-19 periods.In all, 892 patients hospitalized with appendicitis were identified, 241 (27%) in 2020 (Covid period group) and the remaining 651 (73%) during the same calendar periods 2017-2019 (nonCovid period group). Appendicitis during the COVID-19 period was associated with double the risk for undergoing conservative treatment (OR 2.15 [95% CI 1.44-3.21]), and a decreased risk for being diagnosed with perforated appendicitis (OR 0.68 [95% CI 0.48-0.98]).Patients admitted with appendicitis during the early phase of the COVID-19 pandemic in Stockholm, Sweden, were more likely to receive conservative treatment and less likely to suffer from perforated appendicitis compared to patients hospitalized before the pandemic. Hypothetically, this difference could have been due to pandemic-associated resource reallocation, or it may simply reflect an increasing trend towards conservative management of appendicitis.

Background Central obesity is associated with surgical difficulties, but few studies explore the relationship with long-term results after colon cancer surgery. Objective The purpose of this study was to investigate the association between perirenal fat surface area, a proxy for total visceral fat, and oncologic outcome after intestinal resection for colon cancer. Design We investigated the association between perirenal fat surface area (exposure) on recurrence and death (outcome) in patients undergoing surgery with curative intent for colon cancer. Settings The study was conducted at Stockholm South General Hospital, serving a population of 600,000. Patients Patients (N = 733) without metastases at diagnosis who had a preoperative CT and had undergone elective colon resection between 2006 and 2016 were included. Main outcome measures We compared overall survival, recurrence-free survival, and cause-specific survival by perirenal fat surface area. Results Patients with high perirenal fat surface area (fourth quartile) had more often left-sided tumors (45% vs 32% in the first quartile) and experienced more postoperative complications (29% vs 13%), but there were no differences in pathologic T and N stage, radicality of surgery, or adjuvant chemotherapy treatment. Overall survival decreased by increasing cancer stage but was not different between perirenal fat surface area categories. The HR for recurrence-free survival per centimeter squared increase in perirenal fat surface area was 1.00 (95% CI, 0.99-1.01) adjusted for age, sex, ASA category, tumor location, and postoperative complication Clavien-Dindo ≥2. The cumulative incidence of recurrence with death as a competing risk was not statistically different between perirenal fat surface area categories (p = 0.06). Subgroup analyses showed a nonsignificant tendency for men with low perirenal fat surface area to have a lower risk of recurrence and women a higher risk. Limitations In all register-based studies there can be randomly distributed errors. The results can only be generalized to colon resections. Our cohort ranged over a large year span. Conclusions We found no association between perirenal fat surface area and overall survival, recurrence-free survival, or cause-specific cumulative incidence of recurrence in patients undergoing colon resection for cancer. See Video Abstract at http://links.lww.com/DCR/B326. La superficie de grasa perirrenal y el resultado oncolgico en ciruga electiva de cncer de colon ANTECEDENTES:La obesidad central esta asociada con dificultades quirurgicas, pero pocos estudios exploran la relacion de los resultados a largo plazo despues de cirugia de cancer de colon.OBJETIVO:Investigar la asociacion entre la superficie de la grasa perirrenal, como un indicador de la grasa visceral total y el resultado oncologico despues de una reseccion intestinal por cancer de colon.DISENO:Se estudio la asociacion entre el area de la superficie de la grasa perirrenal (expuesta) con la recurrencia y la muerte (resultado) de pacientes sometidos a cirugia con intencion curativa por cancer de colon.AJUSTES:Atencion brindada por el Hospital General del Sur de Estocolmo a una poblacion de 600,000 habitantes.PACIENTES:Aquellos pacientes sin metastasis (n = 733) en el momento del diagnostico que tuvieron una tomografia computada preoperatoria y que se sometieron a una reseccion electiva de colon entre 2006-2016.PRINCIPALES MEDIDAS DE RESULTADO:Comparamos la sobrevida general, la sobrevida libre de recurrencia y la sobrevida especifica de la causa, por area de superficie de grasa perirrenal.RESULTADOS:Los pacientes con una mayor area de superficie de grasa perirrenal (cuarto cuartil) tuvieron mas frecuentemente tumores del lado izquierdo (45% frente a 32% en el primer cuartil) y sufrieron mas complicaciones postoperatorias (29% frente a 13%), pero no hubieron diferencias en el Estadio patologico T y N, ni en lo radical de la cirugia o del tratamiento de quimioterapia adyuvante. La supervivencia general disminuyo al aumentar el estadio del cancer, pero no fue diferente entre las categorias de area de superficie grasa perirrenal. La razon de riesgo para la sobrevida libre de recurrencia por aumento de cm2 en el area de la superficie grasa perirrenal fue de 1.00 (intervalo de confianza del 95%: 0.99-1.01) ajustada por edad, sexo, categoria de la Sociedad Americana de Anestesiologos, ubicacion del tumor y complicacion postoperatoria segun Clavien-Dindo ≥ 2) La incidencia acumulada de recurrencia con muerte como un riesgo competitivo no fue estadisticamente diferente entre las categorias de area de superficie grasa perirrenal (p = 0.06). Los analisis de subgrupos mostraron una tendencia no significativa para que los hombres con un area de superficie menor en grasa perirrenal tengan un menor riesgo de recurrencia y las mujeres un mayor riesgo.LIMITACIONES:En todos los estudios basados en registros puede haber errores distribuidos aleatoriamente. Los resultados solo pueden generalizarse a resecciones de colon. Nuestra cohorte oscilo durante un gran lapso de anos.CONCLUSIONES:No se encontro asociacion entre el area de superficie de la grasa perirrenal y la sobrevida general, ni con la sobrevida libre de recurrencia o la incidencia acumulada de recurrencia especifica de la causa en pacientes sometidos a reseccion de colon por cancer. Consulte Video Resumen en http://links.lww.com/DCR/B326. (Traduccion-Dr Xavier Delgadillo).

Background A substantial proportion of critically ill COVID-19 patients develop thromboembolic complications, but it is unclear whether higher doses of thromboprophylaxis are associated with lower mortality rates. The purpose of the study was to evaluate the association between initial dosing strategy of thromboprophylaxis in critically ill COVID-19 patients and the risk of death, thromboembolism, and bleeding. Method In this retrospective study, all critically ill COVID-19 patients admitted to two intensive care units in March and April 2020 were eligible. Patients were categorized into three groups according to initial daily dose of thromboprophylaxis: low (2500–4500 IU tinzaparin or 2500–5000 IU dalteparin), medium (> 4500 IU but 5000 IU but Results A total of 152 patients were included: 67 received low-, 48 medium-, and 37 high-dose thromboprophylaxis. Baseline characteristics did not differ between groups. For patients who received high-dose prophylaxis, mortality was lower (13.5%) compared to those who received medium dose (25.0%) or low dose (38.8%), p = 0.02. The hazard ratio of death was 0.33 (95% confidence intervals 0.13–0.87) among those who received high dose, and 0.88 (95% confidence intervals 0.43–1.83) among those who received medium dose, as compared to those who received low-dose thromboprophylaxis. There were fewer thromboembolic events in the high (2.7%) vs medium (18.8%) and low-dose thromboprophylaxis (17.9%) groups, p = 0.04. Conclusions Among critically ill COVID-19 patients with respiratory failure, high-dose thromboprophylaxis was associated with a lower risk of death and a lower cumulative incidence of thromboembolic events compared with lower doses. Trial registration Clinicaltrials.gov NCT04412304 June 2, 2020, retrospectively registered.

BACKGROUND: The management of COVID-19 ARDS is debated. Although current evidence does not suggest an atypical acute respiratory distress syndrome (ARDS), the physiological response to prone positioning is not fully understood and it is unclear which patients benefit. We aimed to determine whether proning increases oxygenation and to evaluate responders. METHODS: This case series from a single, tertiary university hospital includes all mechanically ventilated patients with COVID-19 and proning between 17 March 2020 and 19 May 2020. The primary measure was change in PaO2 :FiO2 . RESULTS: Forty-four patients, 32 males/12 females, were treated with proning for a total of 138 sessions, with median (range) two (1-8) sessions. Median (IQR) time for the five sessions was 14 (12-17) hours. In the first session, median (IQR) PaO2 :FiO2 increased from 104 (86-122) to 161 (127-207) mm Hg (P

Background Intraoperative cultures are commonly sent in complicated appendicitis. Culture-guided antibiotics used to prevent postoperative infectious complications are debated. In this study, we describe the microbial overlap between intraoperative and abscess cultures, and antibiotic resistance patterns. Method A local register of a children’s hospital treating children 0–15 years old with appendicitis between 2006 and 2013 was used to find cases with intraoperative cultures, and cultures from drained or aspirated postoperative intraabdominal abscesses. Culture results, administered antibiotics, their nominal coverage of the identified microorganisms, and rationales given for changes in antibiotic regimens were collected from electronic medical records. Results In 25 of 35 patients who met inclusion criteria, there was no overlap between the intraoperative and abscess cultures. In 33 of 35 patients, all identified intraoperative organisms were covered with postoperative antibiotics. In 14 patients, organisms in the abscess culture were not covered by administered antibiotics. Enterococci not found in the intraoperative culture were found in 12 of 35 abscesses. We found no difference in the antibiotic coverage between rationales given for antibiotic changes. Conclusion The overlap between intraoperative cultures and cultures from subsequent abscesses was small. Lack of antibiotic coverage of intraoperative cultures was not an important factor in abscess formation. Electronic supplementary material The online version of this article (10.1007/s00383-018-04428-3) contains supplementary material, which is available to authorized users.

AIM Visceral obesity is associated with perioperative and postoperative complications in colorectal surgery. We aimed to investigate the association between the perirenal fat surface area (PRF) and postoperative complications. METHOD Data on 610 patients undergoing curative, elective colon cancer resection between 2006 and 2016 at Stockholm South General Hospital were retrieved from a local quality register. We assessed perioperative and postoperative outcomes using a multinomial regression model adjusted for age, sex, American Society of Anesthesiologists classification and surgical approach (open/laparoscopy) in relation to PRF. RESULTS PRF could be measured in 605 patients; the median area was 24 cm2 . Patients with PRF ≥ 40 cm2 had longer operation time (median 223 vs 184 min), more intra-operative bleeding (250 vs 125 ml), reoperations (11% vs 6%), surgical complications (27% vs 13%) and nonsurgical infectious complications (16% vs 9%) than patients with PRF < 40 cm2 , but there were no differences in the need for intensive care or duration of hospital stay. The multivariate analyses revealed an increased risk of any complication [OR 1.68 (95% CI 1.1-2.6)], which was even more pronounced for moderate complications [Clavien-Dindo II, OR 2.14 (CI 1.2-2.4]; Clavien-Dindo III, OR 2.35 (CI 1.0-5.5)] in patients with PRF ≥ 40 vs < 40 cm2 . The absolute risk of complications was similar in men and women with PRF ≥ 40 cm2 . CONCLUSION PRF, an easily measured indirect marker of visceral obesity, was associated with overall and moderate complications in men and women and could serve as a useful tool in the assessment of preoperative risk.

Existing data on the safety of out-of-hours cholecystectomy are conflicting. The aim of this study was to investigate whether out-of-hours cholecystectomy for acute cholecystitis is associated with a higher risk for complications compared with surgery during office hours.This was a population-based cohort study. The Swedish Gallstone Surgery and Endoscopic Retrograde Cholangiopancreatography Register (GallRiks) was used to investigate the association between out-of-hours cholecystectomy for acute cholecystitis and complications developing within 30 days. Data from patients who underwent cholecystectomy between 2006 and 2017 were collected. Out-of-hours surgery was defined as surgery commencing between 19.00 and 07.00 hours on weekdays, or any time at weekends (Friday 19.00 hours to Monday 07.00 hours). Multivariable logistic regression analysis was used to assess the risk of complications, with time of procedure as independent variable. The proportion of open procedures and proportion of procedures exceeding 120 min were also analysed. Adjustments were made for sex, age, ASA grade, time between admission and surgery, and hospital-specific features.Of 11 153 procedures included, complications occurred within 30 days in 1573 patients (14·1 per cent). The adjusted odds ratio (OR) for complications for out-of-hours versus office-hours surgery was 1·12 (95 per cent c.i. 0·99 to 1·28). The adjusted OR for procedures completed as open surgery was 1·39 (1·25 to 1·54), and that for operating time exceeding 120 min was 0·63 (0·58 to 0·69).Out-of-hours complications may relate to patient factors and the higher proportion of open procedures.Los datos existentes sobre la seguridad de la colecistectomía fuera del horario laboral son discordantes. El objetivo de este estudio fue investigar si la colecistectomía para el tratamiento de la colecistitis aguda realizada fuera del horario laboral se asocia con un mayor riesgo de complicaciones en comparación con la cirugía efectuada durante el horario laboral. MÉTODOS: Se trata de un estudio de cohortes de base poblacional. Se utilizó el registro Swedish Gallstone Surgery and Endoscopic Retrograde Cholangiopancreatography Register (GallRiks) para examinar la asociación entre la colecistectomía por colecistitis aguda realizada fuera del horario laboral y las complicaciones a los 30 días. Se recogieron los datos de los pacientes en los que se realizó una colecistectomía entre 2006 y 2017. Se definió como cirugía fuera del horario laboral aquella realizada entre las 19:00 y las 07:00 de lunes a viernes y en cualquier momento durante los fines de semana (de viernes 19:00 a lunes 07:00) Se realizó un análisis de regresión logística multivariable para evaluar el riesgo de complicaciones, considerando la hora de la cirugía como variable independiente. También se analizó el porcentaje de intervenciones por vía abierta y el de aquellas cuya duración excedió de los 120 minutos. Se realizaron ajustes por sexo, edad, puntuación ASA, días desde el ingreso hasta la cirugía y características específicas del hospital.Se produjeron 1.573 (14,1%) complicaciones en las 11.153 intervenciones incluidas. La razón de oportunidades, odds ratio (OR) ajustada para las complicaciones comparando la cirugía fuera del horario laboral con la cirugía dentro del horario laboral, fue de 1,12 (i.c. del 95% 0,99-1,28). La OR ajustada para los procedimientos realizado por vía abierta fue de 1,39 (1,25-1,54). La OR ajustada para el tiempo operatorio120 minutos fue de 0,63 (0,58-0,69). CONCLUSIÓN: Las complicaciones que suceden en la cirugía efectuada fuera del horario laboral es más probable que se deban a factores relacionados con el paciente que con la hora del día en que se practica la cirugía. Debe tenerse en cuenta que las intervenciones realizadas por vía abierta fuera del horario laboral tienen una mayor morbilidad.

Purpose Retained foreign rectal objects may require surgical removal. To estimate the magnitude of this problem, we report the incidence and treatment of retained rectal objects at a large emergency hospital, and calculate incidence rates at the national level in Sweden. Methods All local patient records during 2009–2017 with the diagnosis foreign body in anus and rectum (ICD-10 T185) were accessed and analyzed retrospectively. All Swedish in- and outpatient visits during 2005–2016 with the code T185 were accessed from the National Patient Register. Results We show an increasing incidence in rectal foreign bodies in Swedish national data. The increase was most noticeable in men, and in our local register there was an overrepresentation of sex toys leading to laparotomy and stoma. Conclusions To mitigate surgical cost and comorbidity, policies to decrease the risk of retained sex toys could be considered.

Objective: We aimed to evaluate long-term results in patients from regular health care treated with endoscopic transanal closure system, that is, endoscopic vacuum-assisted closure system (EVAC) compared to transanal irrigation. Methods: In this retrospective, medical chart-based, observational study, we included patients with anastomotic leakage after low anterior resection for rectal cancer from 3 Stockholm hospitals 2006–2016 and compared time to first stoma closure in a Kaplan-Meier model and the proportion of patients who were stoma-free at end of follow-up. Results: Anastomotic leakage was found in 81 patients who were followed up in median 5.9 years (min–max: 0.53–13). EVAC was used on 14 (17%) patients and transanal irrigation on 34 (42%) patients. The remaining 33 (41%) patients either got a permanent colostomy or were treated only with antibiotics and percutaneous drainage. Treatment with EVAC or transanal irrigation led to similar rates of stoma closure, both when comparing all patients, and when comparing patients with similar defects. At the end of follow-up, 43% of patients treated with EVAC and 50% of patients treated with repeated irrigation were stoma-free (p = 0.75). Conclusions: We found no evidence of better outcomes in patients treated with EVAC. The study was, however, limited by small sample size.

Cardiolipin is a key lipid component in many biological membranes. Proton conduction and proton-lipid interactions on the membrane surface are thought to be central to mitochondrial energy production. However, details on the cardiolipin headgroup structure are lacking and the protonation state of this lipid at physiological pH is not fully established. Here we present ab initio DFT calculations of the cardiolipin (CL) headgroup and its 2'-deoxy derivative (dCL), with the aim of establishing a connection between structure and acid-base equilibrium in CL. Furthermore, we investigate the effects of solvation on the molecular conformations. In our model, both CL and dCL showed a significant gap between the two pK(a) values, with pK(a2) above the physiological range, and intramolecular hydrogen bonds were found to play a central role in the conformations of both molecules. This behavior was also observed experimentally in CL. Structures derived from the DFT calculations were compared with those obtained experimentally, collected for CL in the Protein Data Bank, and conformations from previous as well as new molecular dynamics simulations of cardiolipin bilayers. Transition states for proton transfer in CL were investigated, and we estimate that protons can exchange between phosphate groups with an approximate 4-5 kcal/mol barrier. Computed NMR and IR spectral properties were found to be in reasonable agreement with experimental results available in the literature.

Cardiolipin is a key lipid component in the inner mitochondrial membrane, where the lipid is involved in energy production, cristae structure, and mechanisms in the apoptotic pathway. In this article we used molecular dynamics computer simulations to investigate cardiolipin and its effect on the structure of lipid bilayers. Three cardiolipin/POPC bilayers with different lipid compositions were simulated: 100, 9.2, and 0% cardiolipin. We found strong association of sodium counterions to the carbonyl groups of both lipid types, leaving in the case of 9.2% cardiolipin virtually no ions in the aqueous compartment. Although binding occurred primarily at the carbonyl position, there was a preference to bind to the carbonyl groups of cardiolipin. Ion binding and the small headgroup of cardiolipin gave a strong ordering of the hydrocarbon chains. We found significant effects in the water dipole orientation and water dipole potential which can compensate for the electrostatic repulsion that otherwise should force charged lipids apart. Several parameters relevant for the molecular structure of cardiolipin were calculated and compared with results from analyses of coarse-grained simulations and available X-ray structural data.

PurposeThe ever present need for the miniaturization of electronic assemblies has driven the size of passive components to as small as the 01005 package size. However, the packaging standards for these components are still under development. The purpose of this work is to report results from experiments designed to establish optimum process parameters, pad sizes and component clearances for the surface mounting of 01005 passive components.Design/methodology/approachThe experiments were designed using MODDE, an experimental design software tool, and were carried out with both 01005 capacitors and resistors. All the assembled components were examined under microscope and judged according to industrial workmanship standards.FindingsIt was found that a viable solder paste printing process for the assembly of 01005 components can be achieved with a 75 μm thick stencil. Type 5 solder paste achieved a similar printing performance to type 4. Under the experimental conditions used, the optimum pad dimensions for the 01005 capacitors were 210 μm length, 220 μm width, 160 μm separation and for the resistors were 190 μm length, 220 μm width, 160 μm separation. The smallest component clearance to reliably avoid bridging was found to be 100 μm. A high placement force of 3.5 N was found to cause cracking of 01005 resistors.Originality/valueFrom this work, a surface mount process for 01005 passive components is established and it is concluded that electronics packaging density can be increased through the assembly of these small components. In the near future, the widespread use of them will definitely facilitate a further reduction in the size of electronic assemblies, especially in handheld and portable devices.

Lipid shape and charge are connected with the physical properties and the biological function of membranes. Cardiolipin, a double phospholipid with four chains and the potential of changing its charge with pH, is crucially connected with mitochondrial inner membrane shape, and recent experiments suggest that local pH changes allow highly curved local geometries. Here, we use a coarse-grained molecular dynamics model to investigate the mechanical properties of cardiolipin bilayers, systematically varying the headgroup charge and the composition in mixtures with zwitterionic 1,2-dioleoyl-glycero-3-phosphatidylcholine (DOPC) or 1,2-dioleoyl-glycero-3-phosphatidylethanolamine (DOPE). Low cardiolipin charge, corresponding to low pH, was found to induce bending moduli on the order of kBT and curved microdomains. On the length scale investigated, in contrast to continuum theoretical models, we found the area modulus and bending modulus to be inversely correlated for mixtures of cardiolipin and DOPC/DOPE, explainable by changes in the effective headgroup volume.

This work highlights four different topics in modeling of DNA: (i) the importance of water and ions together with the structure and function of DNA; the hydration structure around the ions appears to be the determining factor in the ion coordination to DNA, as demonstrated in the results of our MD simulations; (ii) how MD simulations can be used to simulate single molecule manipulation experiments as a complement to reveal the structural dynamics of the studied biomolecules; (iii) how damaged DNA can be studied in computer simulations; and (iv) how repair of damaged DNA can be studied theoretically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

Lipid membranes composed of 1,2-di-(9Z,12Z,15Z)-octadecatrienoyl-3-O-β-D-galactosyl-sn-glycerol or monogalactosyldiacylglycerol (MGDG) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were studied by means of molecular dynamics (MD) computer simulations. Three lipid compositions were considered: 0%, 20%, and 45% MGDG (by mole) denoted as MG-0, MG-20, and MG-45, respectively. The article is focused on the calculation of NMR dipolar interactions, which were confronted with previously reported experimental couplings. Dynamical processes and orientational distributions relevant for the averaging of dipolar interactions were evaluated. Furthermore, several parameters important for characterization of the bilayer structure, molecular organization, and dynamics were investigated. In general, only a minor change in DMPC properties was observed upon the increased MGDG/DMPC ratio, whereas properties related to MGDG undergo a more pronounced change. This effect was ascribed to the fact that DMPC is a bilayer (L(α)) forming lipid, whereas MGDG prefers a reverse hexagonal (H(II)) arrangement.

Cardiolipin (CL) is a negatively charged four acyl chain lipid, associated with energy production in bacterial and mitochondrial membranes. Due to the shape of CL, negative curvatures of aggregates are favorable if the charges in the head group can be reduced. The phase polymorphism of CL, and of associated derivatives with 2, 3, 4, or 5 chains, has been determined previously and offers a model system in which micellar, lamellar, and inverse hexagonal phases can be observed. We present an extension to a previously established coarse-grained molecular dynamics model with the aim of reproducing the different CL phases with two adjustable parameters: the number of acyl chains and the effective head group charge. With molecular dynamics simulations of large lipid systems, we observed transitions between different phases on the nanosecond to microsecond time scale. Charge screening by high salt or low pH was successfully modeled by a reduction of phosphate charge, which led to the adoption of aggregates with more negative curvature. Although specific ion binding at the interface and other atomistic details are sacrificed in the coarse-grained model, we found that it captures general phase features over a large range of aggregate geometries.

Molecular dynamics computer simulations were carried out to study the preferential solvation of phenol in equimolar acetonitrile-water and ethanol-water binary mixtures. Two water models were used to investigate the model dependence of preferential solvation. The results are compared to recent intermolecular 1H NOESY experiments reported on the same systems. In the case of acetonitrile-water the local mole fraction obtained from simulations agrees quite well with experiments. In the case of ethanol-water there was a qualitative difference, which was observed for both water models. However, when comparing the degree of preferential solvation of the two cosolvents ethanol and acetonitrile with each of the two water models, the trend obtained from the simulations agrees with experimental data.

In this chapter we will give short review of computer modelling/simulations of DNA manipulation as a complementary tool to current single molecule manipulation experiments in order to follow the impact on molecular structure during the manipulation experiments. As an example we report molecular dynamics simulations of a 22 base-pair DNA fragment in an explicit water solution with counter-ions to mimic a torsionally unconstrained single-molecule stretching experiment. Positions of the O5′ and O3′ atoms at one end of the 22-mer were fixed while an external linearly increasing tensile force was applied on the corresponding atoms at the other end. Changes in the intramolecular potential energy components reflect large structural changes during the stretching. Large increase in the specific torsional angles of the elongated double-strand DNA is observed as the angles find new stationary values, quite different from those in the dynamically stable original structure before the stretching. Upon pulling the DNA gradually looses its twist developing a spectacular base-stacked structure with the backbones are stretching out in parallel, and the bases were in a zipper-like stack in the position of the major groove of the original un-stretched structure. The results are discussed in the light of recent experiments and some biological consequences of the simulation results are indicated.

This paper presents an investigation of a Volvo Direct Injection Spark Ignition (DISI) engine, where the fuel distribution and the in-cylinder flow field have been mapped by the use of laser techniques in an engine with optical access. Along with the experimental work, CFD-modelling of flow and fuel distribution has been performed.Laser Induced Fluorescence (LIF) visualisation of the fuel distribution in a DI-engine has been performed using an endoscopic detection system. Due to the complex piston crown geometry it was not possible to monitor the critical area around the sparkplug with conventional, through the piston, detection. Therefore, an endoscope inserted in the spark plug hole was used. This approach gave an unrestricted view over the desired area.In addition, the in-cylinder flow fields have been monitored by Particle Image Velocimetry (PIV) through cylinder and piston.The results from both the LIF and the PIV measurements have been compared with CFD-modelling at Volvo. The validation was made at part load when the engine was operating in stratified mode, i.e. late injection during the compression phase. Qualitative agreement was found between the calculated and measured fuel distribution around the spark plug prior to ignition.Also the PIV measurements showed a promising agreement with the flow fields obtained by CFD-modelling. In addition, the transportation properties of the fuel distribution that was monitored by LIF could to a great extent be explained by the results from the PIV measurement and the CFD-modelling.All three techniques showed promising agreements with each other and the measured properties could be used to further increase the accuracy of the CFD-modelling. The close collaboration and comparison between different techniques described in this paper increased the understanding of the processes going on in the combustion chamber. (Less)