Optimal design of a series of cstr's performing reversible reactions catalyzed by soluble enzymes: a theoretical study

The condition for the minimum overall reactor volume of a given number of CSTR's in series is theoretically determined for a reversible, single reactant-single product (Uni-Uni) enzyme catalyzed reaction. The reactor network is assumed to operate in steady-state, isothermal conditions with a single phase and a constant activity of biocatalyst. The method is based on a mathematical analysis of the discrete substrate concentration profile along the CSTR's assuming complete micromixing. The algebraic equations describing the critical loci are obtained for the general case, the mathematical proof that these equations define a minimum is presented, and an exact solution arising from an asymptotic situation is found. An approximate analytical method of optimization based on the aforementioned critical behavior is reported and its validity and usefulness discussed. The formula introduced can be used in more general situations as tools for getting the approximate range where the optimal overall volume of the series of CSTR's lies. Hence, the reasoning developed is important for the preliminary CSTR design and relevant in the initial steps of the more involved methods of numerical optimization. Finally, the enzymatic conversion of fumarate to L-malate is examined as a model system in order to assess the usefulness and applicability of the analysis developed

Average motion of emerging solar active region polarities I: Two phases of emergence

Our goal is to constrain models of active region formation by tracking the average motion of active region polarity pairs as they emerge onto the surface. We measured the motion of the two main opposite polarities in 153 emerging active regions (EARs) using line-of-sight magnetic field observations from the Solar Dynamics Observatory Helioseismic Emerging Active Region (SDO/HEAR) survey (Schunker et al. 2016). We first measured the position of each of the polarities eight hours after emergence and tracked their location forwards and backwards in time. We find that, on average, the polarities emerge with an east-west orientation and the separation speed between the polarities increases. At about 0.1 days after emergence, the average separation speed reaches a peak value of 229 +/- 11 m/s, and then starts to decrease, and about 2.5 days after emergence the polarities stop separating. We also find that the separation and the separation speed in the east-west direction are systematically larger for active regions with higher flux. Our results reveal two phases of the emergence process defined by the rate of change of the separation speed as the polarities move apart. Phase 1 begins when the opposite polarity pairs first appear at the surface, with an east-west alignment and an increasing separation speed. We define Phase 2 to begin when the separation speed starts to decrease, and ends when the polarities have stopped separating. This is consistent with the picture of Chen, Rempel, & Fan (2017): the peak of a flux tube breaks through the surface during Phase 1. During Phase 2 the magnetic field lines are straightened by magnetic tension, so that the polarities continue to move apart, until they eventually lie directly above their anchored subsurface footpoints.Comment: accepted A&

Therapeutic Electromagnetic Field Effects on Angiogenesis and Tumor Growth

Background: A new approach to cancer therapy based on the application of therapeutic electromagnetic fields (TEMF) has been developed by EMF Therapeutics, Inc., Chattanooga, TN, USA. This study was designed to assess the effect of TEMF on tumor vascularization and growth of murine 16/C mammmary adenocarcinoma cells in C3H/HeJ mice. Materials and Methods: Implanted tumors were allowed to grow for seven days until the tumor volume reached 100 mm3 before treatment was started. Mice (20 per control, 10 per EMF exposed group) received treatment (10 minutes per day with 0, 10 mT, 15 mT or 20 mT) with a 120 pulses per second pulsating magnetic field. Tumor growth was assessed throughout the treatment period. The extent of tumor vascularization was evaluated by immrmohistochemical staining for CD31. Results: Exposure to TEMF significantly reduced tumor growth, significantly reduced the percentage of area stained for CD31 indicating a reduction in the extent of vascularization and there was a concomitant increase in the extent of tumor necrosis. Conclusion: A novel TEMF treatment safely reduced growth and vasculadzalion of implanted breast cancers in mice. Implication: TEMF may prove a useful adjuvant to increase the therapeutic index of conventional cancer therapy

Postpneumonectomy syndrome: Surgical management and long-term results

ObjectivePostpneumonectomy syndrome is a rare syndrome of dynamic airway obstruction caused by extreme rotation and shift of the mediastinum after pneumonectomy, resulting in symptomatic central airway compression. We have treated this syndrome by mediastinal repositioning and placement of saline-filled prostheses into the pneumonectomy space. There is a paucity of outcome data for patients treated surgically, with only a single series of 11 patients previously reported. We analyzed our recent experience with treatment of this syndrome and report on the short and long-term outcomes and quality of life assessment of the largest series ever reported of patients treated by mediastinal repositioning.MethodsRecords were reviewed of all patients who underwent mediastinal repositioning for postpneumonectomy syndrome between January of 1992 and June of 2006. Long-term health-related quality of life was assessed by administration of the Saint George's Respiratory Questionnaire.ResultsThere were 18 patients (15 women and 3 men) with a median age of 44 years (range 14–67 years). Thirteen patients had undergone right pneumonectomy, and 5 patients had undergone left pneumonectomy. None of the patients in whom postpneumonectomy syndrome developed after left pneumonectomy had a right-sided aortic arch. Five patients had undergone pneumonectomy in childhood (age < 13 years). The median interval between pneumonectomy and mediastinal repositioning was 7.5 years (range 1.1–54.8 years). The median follow-up was 32 months (range 4–143 months). The operative mortality was 5.6% (1/18). Complications occurred in 5 patients (27.8%): pneumonia in 3 patients and acute respiratory distress syndrome in 2 patients. The median hospitalization was 6 days (range 3–155 days). Some 77% (10/13) of patients reported significant improvement in their breathing and overall state of health after surgery; 15.4% of patients (2/13) were somewhat better, and 7.7% of patients (1/13) had no improvement. No patients' condition was worse after surgery. All patients who reported improvement in their symptoms after surgery remained symptomatically improved at the time of the quality of life assessment. Some 92.3% (12/13) were not at all or only slightly limited in their social activities because of breathing problems, and 84.6% (11/13) were not at all or only slightly limited in their ability to work as a result of their physical health.ConclusionRepositioning of the mediastinum with placement of prostheses for postpneumonectomy syndrome can be performed with low mortality and morbidity. Surgical repositioning provides immediate and lasting symptomatic relief to patients in whom postpneumonectomy syndrome develops

Average motion of emerging solar active region polarities II: Joy's law

The tilt of solar active regions described by Joy's law is essential for converting a toroidal field to a poloidal field in Babcock-Leighton dynamo models. In thin flux tube models the Coriolis force causes Joy's law, acting on east-west flows as they rise towards the surface. Our goal is to measure the evolution of the average tilt angle of hundreds of active regions as they emerge, so that we can constrain the origins of Joy's law. We measured the tilt angle of the primary bipoles in 153 emerging active regions in the Solar Dynamics Observatory Helioseismic Emerging Active Region survey. We used line-of-sight magnetic field measurements averaged over 6 hours to define the polarities and measure the tilt angle up to four days after emergence. We find that at the time of emergence the polarities are on average aligned east-west, and that neither the separation nor the tilt depends on latitude. We do find, however, that ARs at higher latitudes have a faster north-south separation speed than those closer to the equator at the emergence time. After emergence, the tilt angle increases and Joy's law is evident about two days later. The scatter in the tilt angle is independent of flux until about one day after emergence, when higher-flux regions have a smaller scatter in tilt angle than lower-flux regions. Our finding that active regions emerge with an east-west alignment is surprising since thin flux tube models predict that tilt angles of rising flux tubes are generated below the surface. Previously reported tilt angle relaxation of deeply anchored flux tubes can be largely explained by the change in east-west separation. We conclude that Joy's law is caused by an inherent north-south separation speed present when the flux first reaches the surface, and that the scatter in the tilt angle is consistent with buffeting of the polarities by supergranulation.Comment: accepted in Astronomy and Astrophysic

Therapeutic Electromagnetic Field (TEMF) and gamma irradiation on human breast cancer xenograft growth, angiogenesis and metastasis

BACKGROUND: The effects of a rectified semi-sinewave signal (15 mT amplitude, 120 pulses per second, EMF Therapeutics, Inc.) (TEMF) alone and in combination with gamma irradiation (IR) therapy in nude mice bearing a human MDA MB231 breast cancer xenograft were tested. Green fluorescence protein transfected cancer cells were injected into the mammary fat pad of young female mice. Six weeks later, mice were randomly divided into four treatment groups: untreated controls; 10 minute daily TEMF; 200 cGy of IR every other day (total 800 cGy); IR plus daily TEMF. Some mice in each group were euthanized 24 hours after the end of IR. TEMF treatment continued for 3 additional weeks. Tumor sections were stained for: endothelial cells with CD31 and PAS or hypoxia inducible factor 1α (HIF). RESULTS: Most tumors <35 mm(3 )were white but tumors >35 mm(3 )were pink and had a vascularized capsule. The cortex within 100 microns of the capsule had little vascularization. Blood vessels, capillaries, and endothelial pseudopods were found at >100 microns from the capsule (subcortex). Tumors >35 mm(3 )treated with IR 24 hours previously or with TEMF had decreased blood vessels in the subcortex and more endothelial pseudopods projecting into hypoxic, HIF positive areas than tumors from the control group. Mice that received either IR or TEMF had significantly fewer lung metastatic sites and slower tumor growth than did untreated mice. No harmful side effects were attributed to TEMF. CONCLUSION: TEMF therapy provided a safe means for retarding tumor vascularization, growth and metastasis

Anastomotic complications after tracheal resection: Prognostic factors and management

ObjectiveWe sought to identify risk factors for anastomotic complications after tracheal resection and to describe the management of these patients.MethodsThis was a single-institution, retrospective review of 901 patients who underwent tracheal resection.ResultsThe indications for tracheal resection were postintubation tracheal stenosis in 589 patients, tumor in 208, idiopathic laryngotracheal stenosis in 83, and tracheoesophageal fistula in 21. Anastomotic complications occurred in 81 patients (9%). Eleven patients (1%) died after operation, 6 of anastomotic complications and 5 of other causes (odds ratio 13.0, P = .0001 for risk of death after anastomotic complication). At the end of treatment, 853 patients (95%) had a good result, whereas 37 patients (4%) had an airway maintained by tracheostomy or T-tube. The treatments of patients with an anastomotic complication were as follows: multiple dilations (n = 2), temporary tracheostomy (n = 7), temporary T-tube (n = 16), permanent tracheostomy (n = 14), permanent T-tube (n = 20), and reoperation (n = 16). Stepwise multivariable analysis revealed the following predictors of anastomotic complications: reoperation (odds ratio 3.03, 95% confidence interval 1.69-5.43, P = .002), diabetes (odds ratio 3.32, 95% confidence interval 1.76-6.26, P = .002), lengthy (≥4 cm) resections (odds ratio 2.01, 95% confidence interval 1.21-3.35, P = .007), laryngotracheal resection (odds ratio 1.80, 95% confidence interval 1.07-3.01, P = .03), age 17 years or younger (odds ratio 2.26, 95% confidence interval 1.09-4.68, P = .03), and need for tracheostomy before operation (odds ratio 1.79, 95% confidence interval 1.03-3.14, P = .04).ConclusionsTracheal resection is usually successful and has a low mortality. Anastomotic complications are uncommon, and important risk factors are reoperation, diabetes, lengthy resections, laryngotracheal resections, young age (pediatric patients), and the need for tracheostomy before operation

Omentum is highly effective in the management of complex cardiothoracic surgical problems

AbstractObjectives: Vascularized, pedicled tissue flaps are often used for cardiothoracic surgical problems complicated by factors that adversely affect healing, such as previous irradiation, established infection, or steroid use. We reviewed our experience with use of the omentum in these situations to provide a yardstick against which results with other vascularized flaps (specifically muscle flaps) could be compared. Methods: A retrospective review was undertaken of 85 consecutive patients in whom omentum was used in the chest. In 47 patients (group I), use of omentum was prophylactic to aid in the healing of closures or anastomoses considered to be at high risk for failure. In 32 patients (group II), omentum was used in the treatment of problems complicated by established infection. In 6 patients (group III), omentum was used for coverage of prosthetic chest wall replacements after extensive chest wall resection. Results: Overall, omental transposition was successful in its prophylactic or therapeutic purpose in 88% of these difficult cases (75/85). Success with omentum was achieved for 89% of patients (42/47) in group I, 91% of patients (29/32) in group II, and 67% of patients (4/6) in group III. Three patients (3.5%) had complications of omental mobilization. Four patients (4.7%) died after the operation as a result of failure of the omentum to manage the problem for which it was used. Conclusions: Results with omental transposition compare favorably with published series of similarly challenging cases managed with muscle transposition. Complications of omental mobilization are rare. We believe that its unique properties render the omentum an excellent choice of vascularized pedicle in the management of the most complex cardiothoracic surgical problems.J Thorac Cardiovasc Surg 2003;125:526-3

Evidence of Widespread Selection on Standing Variation in Europe at Height-Associated SNPs

Strong signatures of positive selection at newly arising genetic variants are well-documented in humans, but this form of selection may not be widespread in recent human evolution. Because many human traits are highly polygenic and partly determined by common, ancient genetic variation, an alternative model for rapid genetic adaptation has been proposed: weak selection acting on many pre-existing (standing) genetic variants, or polygenic adaptation. By studying height, a classic polygenic trait, we demonstrate the first human signature of widespread selection on standing variation. We show that frequencies of alleles associated with increased height, both at known loci and genome-wide, are systematically elevated in Northern Europeans compared with Southern Europeans $(p<4.3×10^{−4})$. This pattern mirrors intra-European height differences and is not confounded by ancestry or other ascertainment biases. The systematic frequency differences are consistent with the presence of widespread weak selection (selection coefficients $~10^{−3}–10^{−5}$ per allele) rather than genetic drift alone $(p<10^{−15})$

An Upper Mass Limit on a Red Supergiant Progenitor for the Type II-Plateau Supernova SN 2006my

We analyze two pre-supernova (SN) and three post-SN high-resolution images of the site of the Type II-Plateau supernova SN 2006my in an effort to either detect the progenitor star or to constrain its properties. Following image registration, we find that an isolated stellar object is not detected at the location of SN 2006my in either of the two pre-SN images. In the first, an I-band image obtained with the Wide-Field and Planetary Camera 2 on board the Hubble Space Telescope, the offset between the SN 2006my location and a detected source ("Source 1") is too large: > 0.08", which corresponds to a confidence level of non-association of 96% from our most liberal estimates of the transformation and measurement uncertainties. In the second, a similarly obtained V-band image, a source is detected ("Source 2") that has overlap with the SN 2006my location but is definitively an extended object. Through artificial star tests carried out on the precise location of SN 2006my in the images, we derive a 3-sigma upper bound on the luminosity of a red supergiant that could have remained undetected in our pre-SN images of log L/L_Sun = 5.10, which translates to an upper bound on such a star's initial mass of 15 M_Sun from the STARS stellar evolutionary models. Although considered unlikely, we can not rule out the possibility that part of the light comprising Source 1, which exhibits a slight extension relative to other point sources in the image, or part of the light contributing to the extended Source 2, may be due to the progenitor of SN 2006my. Only additional, high-resolution observations of the site taken after SN 2006my has faded beyond detection can confirm or reject these possibilities.Comment: Minor text changes from Version 1. Appendix added detailing the determination of confidence level of non-association of point sources in two registered astronomical image