Salinity regulation of copepod egg production in a large microtidal estuary

Salinity is a key variable for ecological processes in estuaries. Acartia tonsa is a typical estuarine copepod whose responses to salinity have been thoroughly studied in the laboratory. However, results cannot be extrapolated to the field, and formal comparisons between lab and field responses to salinity were not attempted. Here we compare lab-based with field copepod egg production rates (EPR) from the Río de la Plata estuary (RPE), with focus on A. tonsa. Field work was conducted between 2009 and 2011 in the mixing zone of the RPE. Water temperature, salinity and chlorophyll-a varied over ample ranges (temperature: 10.54 - 24.56ºC, salinity: 2.83 - 32.99, chlorophyll-a: 0.62 - 7.27 mg m-3). A. tonsa was the strongly dominant species. EPR ranged between 6.7 and 95.7 eggs female-1 day-1, and correlated to salinity, temperature (weakly), but not to chlorophyll. The relationship between A. tonsa’s EPR (EPRAT) and salinity was consistent with that obtained under laboratory conditions: a humped pattern with a maximum at intermediate salinities. However, differences were also evident, e.g., higher EPRAT was measured in the field. We speculate that discrepancies derive from nutritional differences between field and reference (laboratory) data sets. Besides salinity, food quality and quantity may be first order drivers of A. tonsa’s productivity in the RPE

Motivation at work of Brazilian executives

This study aimed to verify the extent to which the Brazilian executives are motivated at work. Companies seek constantly for practices that allow greater motivation of employees in day-to-day activities. Such search gets particularly important when looking at the work of executives in Brazil, in which working conditions are extremely stressful, whether by race against time, either by issues relating to the relationship among people. Traditional management theory seems to be ineffective when searching for the solution of problems related to the process of management of employees motivation

Hybrid approach to thoracoabdominal aortic aneurysms in patients with prior aortic surgery

none7Objective: The hybrid approach to the repair of thoracoabdominal aortic aneurysm (TAAA), consisting of visceral aortic debranching with retrograde revascularization of the splanchnic and renal arteries and aneurysm exclusion using stent grafts, has been previously described and may be considered particularly appealing in high-risk patients, especially those who have undergone prior aortic surgery. This study analyzed prospectively recorded data of a series of high-risk patients with prior aortic surgery who underwent hybrid TAAA repair at our institute and contrasted the outcomes with those of a similar group of patients who underwent conventional open TAAA repair. Methods: Between 2001 and 2006, 13 patients (12 men) with a median age of 69.6 years (range, 35 to 82 years) underwent one-stage hybrid repair of TAAA (7 type I, 2 type II, 2 type IV, and 2 aneurysms of the visceral aortic patch). These patients, the hybrid group, had a history of aortic surgery (30.7% ascending, 30.7% descending, 46.1% abdominal aortic repair, and 15.4% redo TAAA) and were at high risk for open repair. The criteria used to define these patients as high risk and to indicate the need for hybrid treatment were American Society of Anesthesiologists (ASA) class 3 or 4 associated with a preoperative forced expiratory volume in 1 second (FEV1) <50%. In all cases, we accomplished partial or total visceral aortic debranching through (1) a previous visceral artery retrograde revascularization with synthetic grafts (single bypass, customized Y or bifurcated grafts), and (2) aortic endovascular repair with one of three different commercially produced stent grafts (Cook, W.L. Gore & Assoc, and Medtronic). We analyzed the results and compared the outcomes of the hybrid group with those of a similar group of 29 patients (25 men) with a median age 65.3 years (range, 58 to 79) selected from our overall series of 246 TAAA repairs between 1988 and 2005. These 29 patients, the conventionally treated group, were selected for having had aortic surgery (22% ascending, 38% descending, 42% abdominal aortic repair, and 10.3% redo TAAA), an ASA 3 or 4, a preoperative FEV1 <50%, and a conventional open repair of TAAA (10 type I, 5 type II, 4 type III, 7 type IV, and 3 aneurysms of the visceral aortic patch). Results: In the hybrid group, 32 visceral bypasses were completed and endovascular TAAA repair was successful in all cases. No intraoperative deaths occurred. Perioperative mortality was 23%, and morbidity was 30.8% (renal failure in 2, respiratory failure in 1, and delayed transient paraplegia in 1). At a median follow-up of 14.9 months (range, 11 days to 59.4 months), all grafts were patent at postoperative computed tomography angiography and no aneurysm-related deaths, endoleak, stent graft migration, or morbidity related to visceral revascularization had occurred. No conventionally treated patients died intraoperatively. Perioperative mortality was 17.2% and morbidity was 44.8% (respiratory failure in 7, coagulopathy in 1, renal failure in 2, and paraplegia in 3). At a median follow-up of 5.4 years (range, 1.7 to 7.9 years), no significant complications related to aortic repair occurred, except for three patients (10.3%) with asymptomatic dilatation of the visceral aortic patch <5 cm undergoing radiologic surveillance. Conclusion: Hybrid TAAA repair is technically feasible in selected cases. Perioperative morbidity and mortality were considerable in our subset of high-risk patients with prior aortic surgery, but no aneurysm-related or procedure-related complications were reported at mid-term follow-up. Hybrid TAAA repair did not lead to a significant improvement in outcomes compared with open TAAA repair in a similar group of patients. Larger series are required for valid statistical comparisons and longer follow-ups are necessary to evaluate the durability of hybrid repairs. © 2007 The Society for Vascular Surgery.Chiesa, R.; Tshomba, Y.; Melissano, G.; Marone, E.M.; Bertoglio, L.; Setacci, F.; Calliari, F.Chiesa, R.; Tshomba, Y.; Melissano, G.; Marone, ENRICO MARIA; Bertoglio, L.; Setacci, F.; Calliari, F

The Clumping Transition in Niche Competition: a Robust Critical Phenomenon

We show analytically and numerically that the appearance of lumps and gaps in the distribution of n competing species along a niche axis is a robust phenomenon whenever the finiteness of the niche space is taken into account. In this case depending if the niche width of the species $\sigma$ is above or below a threshold $\sigma_c$, which for large n coincides with 2/n, there are two different regimes. For $\sigma > sigma_c$ the lumpy pattern emerges directly from the dominant eigenvector of the competition matrix because its corresponding eigenvalue becomes negative. For $\sigma </- sigma_c$ the lumpy pattern disappears. Furthermore, this clumping transition exhibits critical slowing down as $\sigma$ is approached from above. We also find that the number of lumps of species vs. $\sigma$ displays a stair-step structure. The positions of these steps are distributed according to a power-law. It is thus straightforward to predict the number of groups that can be packed along a niche axis and it coincides with field measurements for a wide range of the model parameters.Comment: 16 pages, 7 figures; http://iopscience.iop.org/1742-5468/2010/05/P0500

Effect of cold rolling on pitting resistance in duplex stainless steels

Duplex Stainless Steels (DSS) are biphasic austeno-ferritic steels in which the best combination of mechanicaland corrosion-resistance properties is achieved for almost equal volume fractions of the phases. These steelsare classifi ed according to their pitting corrosion resistance, assessed by the PREN index (Pitting ResistanceEquivalent Number) which, although qualitatively, is widely employed as comparison. The present work isaimed to study the pitting resistance of four DSS grades (SAF 2101, 2304, 2205 and 2507) in the as-receivedconditions and after cold rolling at various thickness reductions (from 15% to 85%), to highlight the effects ofcold working on the corrosion behaviour. The materials were potentiodynamically tested in artifi cial seawater(pH 7) and the corresponding Critical Pitting Temperatures (CPT) were determined. Cold deformation mainlyaffected the Lean DSS grades, whereas the high-alloyed DSS were stable, even after heavy deformations.These differences can be attributed not only to composition but also to the onset of diffusionless phasetransformations induced by cold working, which make the materials more prone to corrosive attacks

Caratterizzazione microstrutturale di nummi ufficiali e imitativi del V secolo d.C.

La riforma di Costantino del 309 d.C. introdusse il sistema monetario basato sulla moneta d’oro, con la qualecoesistevano, però, anche nominali d’argento e in leghe di rame: questi ultimi, denominati nummi, subironotra la fine del IV e il V secolo d. C. una netta riduzione ponderale in seguito alla quale raggiunsero pesi ancheinferiori al grammo. Nel presente lavoro sono stati caratterizzati un gruppo di nummi “bronzei” allo scopo dideterminarne la composizione chimica e la struttura metallurgica da correlare alla tecnologia di produzione.Sono state applicate tecniche microscopiche (SEM-EDS) su sezioni metallografiche e spettroscopiche (XRF) sucampioni integri. I dati ottenuti con le diverse tecniche evidenziano che le monete in bronzo, con alti tenori diPb, sono state prodotte per deformazione plastica di tondelli ottenuti per fusione entro matrici refrattarie.I valori percentuali delle componenti della lega Cu-Sn, con aggiunte di Pb, rientrano nell’intervallo dicomposizione di monete bronzee tardoantiche di ambito occidentale

Trattamenti di ricottura dell’acciaio inossidabile duplex 2205 dopo deformazione plastica

Le buone caratteristiche meccaniche e le elevate proprietà di resistenza a corrosione spiegano il vasto utilizzodegli inossidabili duplex in ambito chimico, petrolchimico e strutturale i duplex sono, però soggetti aprecipitazione di fasi secondarie, che ne degradano le proprietà, negli intervalli di temperatura 500-1000°C.In questo lavoro si è analizzata l’influenza del trattamento isotermico nell’intervallo 850-900°C sulletrasformazioni di fase per l’acciaio 2205 deformato a freddo.La lega è stata sottoposta a deformazioni a freddo con una riduzione di spessore del 5%, 10%, 15%; in seguitoa trattamenti termici presenta precipitazione di fasi deleterie ? e ?. Si è analizzata l’evoluzione dellaprecipitazione in funzione del grado di deformazione e del tempo di trattamento, mediante microscopia otticaed elettronica. Mediante software d’analisi d’immagine è stata realizzata la quantificazione delle fasiprecipitate. I risultati ottenuti hanno rivelato che il materiale deformato a freddo è molto più sensibile allaprecipitazione di fasi secondarie rispetto al materiale allo stato solubilizzato ed al conseguente infragilimentodopo brevi soste nell’intervallo di temperatura critico per la precipitazione

Mixed ab initio quantum mechanical and Monte Carlo calculations of secondary emission from SiO2 nanoclusters

A mixed quantum mechanical and Monte Carlo method for calculating Auger spectra from nanoclusters is presented. The approach, based on a cluster method, consists of two steps. Ab initio quantum mechanical calculations are first performed to obtain accurate energy and probability distributions of the generated Auger electrons. In a second step, using the calculated line shape as electron source, the Monte Carlo method is used to simulate the effect of inelastic losses on the original Auger line shape. The resulting spectrum can be directly compared to 'as-acquired' experimental spectra, thus avoiding background subtraction or deconvolution procedures. As a case study, the O K-LL spectrum from solid SiO2 is considered. Spectra computed before or after the electron has traveled through the solid, i.e., unaffected or affected by extrinsic energy losses, are compared to the pertinent experimental spectra measured within our group. Both transition energies and relative intensities are well reproduced.Comment: 9 pageg, 5 figure

Precision measurements of Linear Scattering Density using Muon Tomography

We demonstrate that muon tomography can be used to precisely measure the properties of various materials. The materials which have been considered have been extracted from an experimental blast furnace, including carbon (coke) and iron oxides, for which measurements of the linear scattering density relative to the mass density have been performed with an absolute precision of 10%. We report the procedures that are used in order to obtain such precision, and a discussion is presented to address the expected performance of the technique when applied to heavier materials. The results we obtain do not depend on the specific type of material considered and therefore they can be extended to any application.Comment: 16 pages, 4 figure