The water supercooled regime as described by four common water models

The temperature scale of simple water models in general does not coincide with the natural one. Therefore, in order to make a meaningful evaluation of different water models a temperature rescaling is necessary. In this paper we introduce a rescaling using the melting temperature and the temperature corresponding to the maximum of the heat capacity to evaluate four common water models (TIP4P-Ew, TIP4P-2005, TIP5P-Ew and Six-Sites) in the supercooled regime. Although all the models show the same general qualitative behavior, the TIP5P-Ew appears as the best representation of the supercooled regime when the rescaled temperature is used. We also analyze, using thermodynamic arguments, the critical nucleus size for ice growth. Finally, we speculate on the possible reasons why atomistic models do not usually crystalize while the coarse grained mW model do crystallize.Comment: 8 pages, 8 figure

The Sound of Topology in the AdS/CFT Correspondence

Using the gauge/gravity correspondence, we study the properties of 2-point correlation functions of finite-temperature strongly coupled gauge field theories, defined on a curved space of general spatial topology with a dual black hole description. We derive approximate asymptotic expressions for the correlation functions and their poles, supported by exact numerical calculations, and study their dependence on the dimension of spacetime and the spatial topology. The asymptotic structure of the correlation functions depends on the relation between the spatial curvature and the temperature, and is noticeable when they are of the same order. In the case of a hyperbolic topology, a specific temperature is identified for which exact analytical solutions exist for all types of perturbations. The asymptotic structure of the correlation functions poles is found to behave in a non-smooth manner when approaching this temperature.Comment: 65 pages, LaTeX, 21 figures, 1 table; fixed a small error in subsection 3.

Annular-shaped emission from gallium nitride nanotube lasers

Annular-shaped lasing emission is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observe a clear threshold of 1055 kW/cm2, a narrow spectral linewidth of 0.19 nm, and guided emission from the nanotubes. Lasing is also demonstrated in a liquid environment, with an approximate doubling in threshold observed. The nanotube lasers could be of interest for optical nanofluidic applications or applications benefiting from a hollow beam shape. More generally, the results indicate that cross-sectional shape control can be employed to manipulate the properties of nanolasers

Polarization control in GaN nanowire lasers

We demonstrate polarization control in optically-pumped single GaN nanowire lasers fabricated by a top-down method. By placing the GaN nanowires onto gold substrates, the naturally occurring randomly orientated elliptical polarization of nanowire lasers is converted to a linear polarization that is oriented parallel to the substrate surface. Confirmed by simulation results, this polarization control is attributed to a polarization-dependent loss induced by the gold substrate, which breaks the mode degeneracy of the nanowire and forms two orthogonally polarized modes with largely different cavity losses

Identifying trade-offs and reference points in support of ecosystem approaches to managing Gulf of Mexico menhaden

Gulf menhaden (Brevoortia patronus) support the largest fishery by yield in the Gulf of Mexico (GoM) and are a key forage species for many marine predators. While menhaden stock assessments indicated that overfishing was not likely to have occurred in the past, concerns have been raised regarding the possible effects of menhaden fishing on their predators. In this study, we used a US Gulfwide Ecopath with Ecosim (EwE) model to explore the predicted effects of increased menhaden harvest on the GoM ecosystem and focused our analyses on Gulf menhaden predators. Key menhaden predators identified included king mackerel (Scomberomorus cavalla), Spanish mackerel (Scomberomorus maculatus), sea trout (Cynoscion spp.), red drum (Sciaenops ocellatus), and pelagic coastal piscivores [e.g., bluefish (Pomatomus saltatrix)]. As expected, these predators exhibited reduced biomass in response to increased Gulf menhaden harvest, with a predicted 11% decrease in predator biomass at simulated fishing levels near historical highs. Our results indicate strong relationships between the effects of menhaden fishing and the predator fishing mortality for king mackerel and intermediate relationships for Spanish mackerel, blacktip shark (Carcharhinus limbatus), red drum, large coastal sharks, and pelagic coastal piscivores. Biomass of predator groups such as demersal coastal invertebrate feeders [e.g., drums and croakers (Sciaenidae)] are more affected by menhaden harvest (through trophodynamics interactions and bycatch removal) compared to the isolated effect of their fishing mortality. For almost all the groups examined in the trade-off analysis, with the exception of sea trout, current biomass (2016) was higher than their target biomass representing 75% of their biomass at maximum sustainable yield. In comparison to the time series of fishing mortality rates estimated by the most recent Gulf menhaden stock assessment, the mean ecological reference point (ERP) of 0.862 was exceeded in all but 1 year from 1977 to 2007; however, neither the target nor threshold upper ERP value has been exceeded since 2008. The observed Gulf menhaden landings from 2003 to the present were generally within the range of the projected equilibrium landings (i.e., within confidence intervals) at both the ERP target and threshold values except for three recent years

Acylglycerol Recycling from Triacylglycerol to Phospholipid, Not Lipase Activity, Is Defective in Neutral Lipid Storage Disease Fibroblasts

Neutral lipid storage disease (NLSD) is an autosomal recessive disorder in which excess triacylglycerol (TG) accumulates in most cells. Although it has been hypothesized that the TG accumulation is caused by a functional defect in cytosolic lipase activity, we were able to expose TG hydrolysis in NLSD cells by using triacsin C, an inhibitor of acyl-CoA synthetase that blocks the reincorporation of hydrolyzed fatty acids into glycerolipids. Our data suggest that TG lipolysis in NLSD cells is masked by rapid TG resynthesis, occurring because released acylglycerols cannot be used for phospholipid synthesis. In uptake studies, triacsin C blocked the incorporation of [3H]glycerol into glycerolipids, incorporation of [14C]oleate into TG, but not incorporation of [14C]oleate into phospholipid. Thus, the drug inhibited both de novo synthesis of glycerolipids via the glycerol-3-phosphate pathway and the synthesis of TG from diacylglycerol. The drug did not appear to block reacylation of lysophospholipids. Triacsin C caused a loss of about 60% of the TG mass from both NLSD and oleate-loaded control cells. Rates of TG lipolysis were similar in NLSD cells and oleate-loaded control cells labeled with [6-(7-nitro-2,1,3-benzoxadiazol-4-yl)-amino]hexanoic acid or labeled with [14C]oleate or [3H]glycerol and chased in the presence of triacsin C. During a 96-h chase, [14C]oleate reincorporation into the different phospholipid species increased only in control cells. Similar results were observed when NLSD, and control cells were chased after labeling with [3H]glycerol. These data strongly suggest that normal human fibroblasts mobilize stored TG for phospholipid synthesis and that recycling to PC occurs via a TG-derived mono- or diacylglycerol intermediate. Normal recycling to phosphatidylethanolamine may primarily involve TG-derived acyl groups rather than an acylglycerol precursor. NLSD cells appear to have a block in this recycling pathway with the result that both hydrolyzed fatty acids and the acylglycerol backbone are re-esterified to form TG. Because the NLSD phenotype includes ichthyosis, fatty liver, myopathy, cardiomyopathy, and mental retardation, the recycling pathway appears to be critical for the normal function of skin, liver, muscle, heart, and the central nervous system

Donor Complications Following Laparoscopic Compared to Hand-Assisted Living Donor Nephrectomy: An Analysis of the Literature

There are two approaches to laparoscopic donor nephrectomy: standard laparoscopic donor nephrectomy (LDN) and hand-assisted laparoscopic donor nephrectomy (HALDN). In this study we report the operative statistics and donor complications associated with LDN and HALDN from large-center peer-reviewed publications. Methods. We conducted PubMed and Ovid searches to identify LDN and HALDN outcome studies that were published after 2004. Results. There were 37 peer-reviewed studies, each with more than 150 patients. Cumulatively, over 9000 patients were included in this study. LDN donors experienced a higher rate of intraoperative complications than HALDN donors (5.2% versus. 2.0%, P < .001). Investigators did not report a significant difference in the rate of major postoperative complications between the two groups (LDN 0.5% versus HALDN 0.7%, P = .111). However, conversion to open procedures from vascular injury was reported more frequently in LDN procedures (0.8% versus 0.4%, P = .047). Conclusion. At present there is no evidence to support the use of one laparoscopic approach in preference to the other. There are trends in the data suggesting that intraoperative injuries are more common in LDN while minor postoperative complications are more common in HALDN

Diacylglycerol generated in CHO cell plasma membrane by phospholipase C is used for triacylglycerol synthesis

The diacylglycerol (DAG) signal generated from membrane phospholipids by hormone-activated phospholipases is attenuated by mechanisms that include lipolysis or phospholipid resynthesis. To determine whether the DAG signal might also be terminated by incorporation of DAG into triacylglycerol (TAG), we studied the direct formation of TAG from endogenous DAG generated by bacterial phospholipase C (PLC). When Chinese hamster ovary (CHO) cells prelabeled with