Different Mechanisms For Production Research Articles

A new approach to include surface tension in the subgrid eddy viscosity for the two-phase LES

Turbulent two-phase flows feature different mechanisms for production and dissipation of turbulent kinetic energy compared to the single-phase flows. However, this difference is usually neglected in developing eddy viscosity-based subgrid scale (SGS) models for the two-phase large eddy simulation (LES). In this study, a new approach is presented for the two-phase LES to include the surface tension, which is a production mechanism for the kinetic energy in the small scale motions, into the subgrid eddy viscosity model. We follow the Favre-filtered governing equations of interfacial flows based on the volume of fluid (VOF) approach and derive the transport equation for the turbulent kinetic energy to include the effect of surface tension. The original contribution of this study is to propose a new form for the eddy viscosity based on the mixing length assumption which includes an additional production mechanism of turbulent kinetic energy stemming from the interfacial work i.e. surface tension. The proposed model for eddy viscosity is employed to close all the SGS terms. The model performance is evaluated by means of the a-priori filtering of the fine grid simulation of phase inversion problem. To test the generality of the model at different physical conditions, two different density ratios were considered for the fine grid simulation. The results highlight a significant improvement of the eddy viscosity-based SGS models in prediction of the turbulent kinetic energy for the small unresolved scales particularly for the regions of low shear. Furthermore, the model appears to perform more accurately in the case of low density ratios. This study provides a proper perspective for future SGS models in the context of large eddy simulation of two-phase flows.

Cholesterol oversynthesis markers define familial combined hyperlipidemia versus other genetic hypercholesterolemias independently of body weight

Primary hypercholesterolemia of genetic origin, negative for mutations in LDLR, APOB, PCSK9 and APOE genes (non-FH GH), and familial combined hyperlipidemia (FCHL) are polygenic genetic diseases that occur with hypercholesterolemia, and both share a very high cardiovascular risk. In order to better characterize the metabolic abnormalities associated with these primary hypercholesterolemias, we used noncholesterol sterols, as markers of cholesterol metabolism, to determine their potential differences. Hepatic cholesterol synthesis markers (desmosterol and lanosterol) and intestinal cholesterol absorption markers (sitosterol and campesterol) were determined in non-FH GH (n=200), FCHL (n=100) and genetically defined heterozygous familial hypercholesterolemia subjects (FH) (n=100) and in normolipidemic controls (n=100). FCHL subjects had lower cholesterol absorption and higher cholesterol synthesis than non-FH GH, FH and controls (P<.001). When noncholesterol sterols were adjusted by body mass index (BMI), FCHL subjects had higher cholesterol synthesis than non-FG GH, FH and controls (P<.001). An increase in BMI was accompanied by increased cholesterol synthesis and decreased cholesterol absorption in non-FH GH, FH and controls. However, this association between BMI and cholesterol synthesis was not observed in FCHL. Non-high-density-lipoprotein cholesterol showed a positive correlation with cholesterol synthesis markers similar to that of BMI in non-FH GH, FH and normolipemic controls, but there was no correlation in FCHL. These results suggest that FCHL and non-FH GH have different mechanisms of production. Cholesterol synthesis and absorption are dependent of BMI in non-FH GH, but cholesterol synthesis is increased as a pathogenic mechanism in FCHL independently of age, gender, APOE and BMI.

Parures annulaires massives à décor incisé du Bronze moyen au Nord-Ouest de la France (Bretagne, Pays de la Loire, Basse-Normandie). Pour une remise en question du type de Bignan

Au cours du Bronze moyen, la production metallique est caracterisee, entre autres, par la diffusion de parures annulaires originales, massives et portant un riche decor incise, qui constituent la forme de parure majoritaire au sein des depots de cette periode en France de l’Ouest. J. Briard (1965) fut le premier a individualiser ces objets, auxquels il donna le nom de bracelets du type de Bignan, d’apres un depot morbihannais en contenant dix-huit exemplaires. Presents tres frequemment dans les depots du Massif armoricain, ces objets sont depuis indistinctement designes ainsi lors de leur decouverte. Il semble desormais necessaire de revenir sur cette denomination, qui regroupe des productions parfois tres differentes, et qui ne permet pas la prise en compte des particularismes morphologiques et decoratifs regionaux. La presente etude concerne les parures annulaires decouvertes en Bretagne, Pays de la Loire et Basse-Normandie, une aire geographique formant une zone relativement homogene pour ce type de productions. Les regions Haute-Normandie, Poitou-Charentes, Aquitaine, Ile-de-France et le Sud de l’Angleterre ont livre des objets relativement proches, mais dont la morphologie et le decor se distinguent cependant par des caracteristiques regionales propres. Ils seront donc egalement etudies ici afin de replacer le Nord-Ouest francais au sein d’un phenomene qui apparait generalise a l’ensemble de l’Europe atlantique. Il convient aujourd’hui de determiner les ressemblances et differences existant entre les zones de concentration de ces objets, ainsi que de tenter d’en deceler les mecanismes de production, d’utilisation, d’echange et de depot. L’etude precise de la repartition geographique, des contextes de decouverte, des caracteres morphologiques et decoratifs de ces elements de parure permet de proposer une classification renouvelee ainsi que la definition de plusieurs groupes de production. Les differentes zones geographiques etudiees ici presentent des combinaisons preferentielles de criteres morphologiques et decoratifs, liees a des choix techniques, symboliques ou esthetiques, necessitant une reprise des donnees concernant la typologie et la terminologie des bracelets du type de Bignan.

Angular ion emission characteristics of a laser triggered tin vacuum arc as light source for extreme ultraviolet lithography

The angular resolved emission of tin ions from a laser triggered vacuum arc to be used as light source for extreme ultraviolet lithography is presented. Ion energies of more than 200 keV for emission angles up to 50° with respect to the optical axis are observed. The angular emission characteristic is strongly anisotropic with a pronounced peak for fast ions into a cone with an opening angle of roughly 10° at an angle of 35° with respect to the optical axis. These ions also exhibit a distinct energy distribution function compared to the more isotropic emitted bulk of ions, which can be referred to different mechanisms of production. Looking at the discharge current parameters, the production of the directed fast ions can be connected with a peaked increase in the impedance, which gives hint to a plasma instability as origin of those ions. The emission of isotropic emitted ions is in agreement with a model of plasma expansion into vacuum. The emission characteristic is also strongly dependent on the parameter of the trigger laser. It is shown that using a double trigger laser pulse the fast ion production can be suppressed by more than one order of magnitude.

The effect of dexamethasone on symptom burden in patients with advanced cancer.

TPS318 Background: Patients with advanced cancer experience severe physical and psychosocial symptoms (fatigue, pain, anorexia, and nausea) and this symptom burden reduces quality of life. The symptom expression is a multidimensional construct that results from different mechanisms of production and brain perception. Circulating cytokines (IL-6, IL-1b, TNF-alpha, IL-10, and IL-8) have been associated with fatigue, pain, anorexia, and nausea. There are limited treatment options to manage the overall symptom burden. Corticosteroids such as dexamethasone have been widely used in the treatment of fatigue, pain, anorexia, and nausea. But to date there are no well-powered placebo-controlled trials to draw definitive conclusions with regard to efficacy in management of these symptoms. In addition, not all assessment tools used were validated and there was no attempt to understand the pathophysiology using laboratory correlates. The objective of this prospective, randomized, double-blind, placebo-controlled study is to compare the effect of dexamethasone versus placebo to study its effect on cancer-related symptom burden and the association of dexamethasone in reducing the inflammatory cytokine levels and thereby symptom burden using validated tools and laboratory correlates. Methods: Advanced cancer patients with fatigue, pain, nausea, or anorexia greater than ≥ 4/10 on the Edmonton Symptom Assessment Scale (ESAS), normal cognition, no infections and hemoglobin ≥ 9 g are eligible for enrollment. 125 eligible patients are randomized to dexamethasone 4 mg orally two times a day for 14 days (primary end point) or matching placebo. On day 15, all patients receive dexamethasone 4 mg orally twice a day for 7 days, and then the dose of dexamethasone is tapered to 2 mg orally twice a day between days 22 to 28. All patients are off study on day 29. During the study period, patients will be assessed for the intensity of fatigue, pain, anorexia and nausea and other symptoms and toxicities. Patients undergo serial weekly assessments such as FACIT-F, cytokine levels (IL-1, IL-6, TNF- alpha,IL-10, IL-8, activated monocytes) and CRP levels. Current enrollment: To date 59 eligible patients with advanced cancer are enrolled. No significant financial relationships to disclose.

Production of exotic Λ hypernuclei via mesonic beams

We study the production of neutron-rich hypernuclei Λ 12 Be, Λ 16 C, and Λ 10 Li by the (π −, K +) and (K −, π +) reactions in flight and treat two different mechanisms of production. The first mechanism is a two-step process with meson charge exchange (e.g., π − p → π 0 n, π 0 p → K +Λ). The other mechanism is one-step production (π − p → K +Σ−) proceeding via a small Σ− component, arising in Λ hypernuclei due to ΛN–ΣN coupling, as a doorway state. Typically, the two-step mechanism is more productive. The forward differential cross section of the 10B(π −,K +) reaction is about 70 nb/sr at an incident momentum of 1.05 GeV/c. On the other hand, the one-step process can serve as a direct measurement of the Σ admixture if the two-step contribution is suppressed by a suitable choice of the reaction kinematics.

Delayed pneumocephalus in shunted patients. Report of three cases and review of the literature

Delayed pneumocephalus is a very rare complication of CSF shunt systems with only 37 cases so far reported. We report three additional cases with different mechanisms of production, clinical presentations and managements. While the first patient was treated with closure of the site of air entrance and shunt externalization, in the second case, modification of the shunt was enough to solve the pneumocephalus, even when a skull base fistula was suspected. The third one died during treatment from complications. The literature is reviewed with respect to the aetiology, clinical presentation, radiological findings and management of this problem.

Expression of the fibrinogen genes in rat megakaryocytes

A variety of evidence suggests that megakaryocytes synthesize fibrinogen and comparative immunochemical and structural studies indicate that fibrinogen produced in or associated with megakaryocytes may be different than fibrinogen produced in the liver. Two studies have reported that the γ′ chain, which is produced from the γ chain gene by alternative splicing, is absent from fibrinogen produced in the megakaryocyte. Since there is only a single gene for each of the three fibrinogen chains the reported structural differences suggest different mechanisms for production of hepatic and megakaryocytic fibrinogen. We have begun an investigation of the varying mechanisms for expression of the fibrinogen genes by examining the structure of fibrinogen mRNA's in the two tissues. Fibrinogen mRNA's of identical length are found in both liver and megakaryocytes. Furthermore, despite the reported absence of the γ′ chain in platelet-associated fibrinogen, we have used a probe specific for the alternative spliced region of the γ′ mRNA to clearly demonstrate this chain in megakaryocyte mRNA. These studies indicate that the γ′ mRNA is either not translated in platelets or that the γ′ chain is unable to associate with the α and β chains to form a mature molecule.

Slow ventricular tachycardia complicating acute myocardial infarction.

Among 200 consecutive cases of acute myocardial infarction (AMI) treated in a CCU, 117 episodes of slow ventricular tachycardia were observed in 72 patients. This figure represents a 36% rate of incidence. It is a relatively high figure because of the close monitoring to which the patient is submitted and because of the early admission to the unit. There were no significant differences of age, sex, or localization of the myocardial necrosis between patients with SVT and those without it. The different mechanisms of production described support an active origin in most of the patients for the following reasons: (1) coexistence of SVT and PVT in 51.3% of the patients; (2) identical QRS morphology in both rhythms; (3) onset of the SVT after a nonprolonged diastole in 70% of the tracings; (4) inhibition of the SVT after increase of the sinus discharge in only 14 occasions; and (5) irregular SVT rhythm in 76.9% of the recordings and ectopic mechanisms with different degrees of exit block. Because of the potential hazard of the SVT, especially if it is assumed to be of an active origin, we recommend lidocaine for patients with a sinus rate faster than 60 per minute or coexisting PVT. Atropine should be used when the sinus rate is slower than 60 per minute assuming a possible escape or passive origin.

Neutrophil kinetics in hereditary and congenital neutropenias.

Neutrophil production and distribution were studied in two families with autosomal dominantly inherited neutropenia to distinguish their illness from other neutropenic disorders. In addition to a reduced post-mitotic pool of bone-marrow neutrophils and neutrophil precursors, mitotic pool size was also reduced, ranging from 1.1 to 2.9 X 10(9) cells per kilogram (normal, 3.8 +/- 0.4 X 10(9) per kilogram). In vitro committed stem cells were reduced as well, ranging from 2 to 12/10(5) marrow cells (normal, 30 to 120/10(5)). In three patients neutrophil counts were observed to return to normal when they were adults. In one such subject studied, however, both the mitotic pool of neutrophil precursors and marrow committed stem cells were reduced. These abnormalities were in contrast to studies of a patient with chronic benign neutropenia of childhood and an infant with Kostmann-type congenital neutropenia, both of whom had increased marrow committed stem cells. These studies demonstrate several different mechanisms for production of neutropenia in these syndromes.

Automaticity and automatic rhythms

The nature of the automatic process in cardiac pacemakers is discussed with special reference to the mechanism of diastolic depolarization in cardiac Purkinje fibers as investigated by the use of the voltage clamp technique. The major factors controlling cardiac automaticity—the sympathetic nerves, the vagi and overdrive suppression —are analyzed. Under different conditions, both sympathetic and vagus nerve stimulation can lead to a slowing or acceleration of cardiac pacemakers. The mechanism by which the sympathetic nerves can slow and the vagus nerve accelerate the pacemaker rate is reported. The inhibition exerted by the sinus node on idioventricular pacemakers through overdrive suppression is described: Overdrive suppression is a form of inhibition that operates when a pacemaker is driven at a rate faster than its own. The mechanism of overdrive suppression is indicated by a frequency-dependent electrogenic sodium extrusion. Automatic rhythms are classified according to different mechanisms of production; they can result from an exaggeration of the normal automatic process or from mechanisms absent under normal conditions. Examples of different arrhythmias are given, and it is noted that some types of tachycardias can occur while automaticity is depressed.