The effect of Nafion film on the cathode catalyst layer performance in a low-Pt PEM fuel cell

A single--pore model for performance of the cathode catalyst layer (CCL) in a PEM fuel cell is developed. The model takes into account oxygen transport though the CCL depth and through the thin Nafion film, separating the pore from Pt/C species. Analytical solution to model equations reveals the limiting current density $j_N^{\rm lim}$ due to oxygen transport through the Nafion film. Further, $j_N^{\rm lim}$ linearly depends of the CCL thickness, i.e., the thinner the CCL, the lower $j_N^{\rm lim}$. This result may explain unexpected lowering of low--Pt loaded catalyst layers performance, which has been widely discussing in literature.Comment: 11 page

The Critical Coupling Likelihood Method: A new approach for seamless integration of environmental and operating conditions of gravitational wave detectors into gravitational wave searches

Any search effort for gravitational waves (GW) using interferometric detectors like LIGO needs to be able to identify if and when noise is coupling into the detector's output signal. The Critical Coupling Likelihood (CCL) method has been developed to characterize potential noise coupling and in the future aid GW search efforts. By testing two hypotheses about pairs of channels, CCL is able to identify undesirable coupled instrumental noise from potential GW candidates. Our preliminary results show that CCL can associate up to $\sim 80$ of observed artifacts with $SNR \geq 8$, to local noise sources, while reducing the duty cycle of the instrument by $\lesssim 15$. An approach like CCL will become increasingly important as GW research moves into the Advanced LIGO era, going from the first GW detection to GW astronomy.Comment: submitted CQ

Self-dual supersymmetric nonlinear sigma models

In four-dimensional N=1 Minkowski superspace, general nonlinear sigma models with four-dimensional target spaces may be realised in term of CCL (chiral and complex linear) dynamical variables which consist of a chiral scalar, a complex linear scalar and their conjugate superfields. Here we introduce CCL sigma models that are invariant under U(1) "duality rotations" exchanging the dynamical variables and their equations of motion. The Lagrangians of such sigma models prove to obey a partial differential equation that is analogous to the self-duality equation obeyed by U(1) duality invariant models for nonlinear electrodynamics. These sigma models are self-dual under a Legendre transformation that simultaneously dualises (i) the chiral multiplet into a complex linear one; and (ii) the complex linear multiplet into a chiral one. Any CCL sigma model possesses a dual formulation given in terms of two chiral multiplets. The U(1) duality invariance of the CCL sigma model proves to be equivalent, in the dual chiral formulation, to a manifest U(1) invariance rotating the two chiral scalars. Since the target space has a holomorphic Killing vector, the sigma model possesses a third formulation realised in terms of a chiral multiplet and a tensor multiplet. The family of U(1) duality invariant CCL sigma models includes a subset of N=2 supersymmetric theories. Their target spaces are hyper Kahler manifolds with a non-zero Killing vector field. In the case that the Killing vector field is triholomorphic, the sigma model admits a dual formulation in terms of a self-interacting off-shell N=2 tensor multiplet. We also identify a subset of CCL sigma models which are in a one-to-one correspondence with the U(1) duality invariant models for nonlinear electrodynamics. The target space isometry group for these sigma models contains a subgroup U(1) x U(1).Comment: 22 page

Lipase activity in vesicular systems: Characterization of candida cylindracea lipase and its activity in polymerizable dialkylammonium surfactant vesicles

Lipase from Candida cylindracea (CCL) was incorporated into polymerizable positively charged dialkylammonium bromide surfactant vesicles. The enzyme was incorporated by the use of the dehydration-rehydration method or by incubation. In the latter case, trapping efficiencies of up to 100% could be obtained. Activities of free and vesicle-incorporated CCL were tested for three triglycerides: triacetin, tributyrin, and tricaprylin. Enzyme activity was lowest in homogeneous mixtures (triacetin and small concentrations of tributyrin) and highest in heterogeneous mixtures (tricaprylin and high concentrations of tributyrin). Entrapment in vesicular systems is advantageous, especially in homogeneous reaction mixtures and in the case of the production of insoluble fatty acid (caproate), because inhibition by the acid can be suppressed. The influence of several surface-active additives, including vesicles, on the activity of lipase in triglyceride assays was tested. Vesicles have a positive influence on the activity, whereas other positively charged additives act as inhibitors. In the case of tricaprylin assays, the positively charged additives increase the activity. Finally, tryptic digestion for free and incorporated CCL were compared. Free CCL is readily inactivated, whereas incorporated enzyme is protected from proteolytic degradation

Effects of Parasitics and Interface Traps On Ballistic Nanowire FET In The Ultimate Quantum Capacitance Limit

In this paper, we focus on the performance of a nanowire Field Effect Transistor (FET) in the Ultimate Quantum Capacitance Limit (UQCL) (where only one subband is occupied) in the presence of interface traps ($D_{it}$), parasitic capacitance ($C_L$) and source/drain series resistance ($R_{s,d}$) using a ballistic transport model and compare the performance with its Classical Capacitance Limit (CCL) counterpart. We discuss four different aspects relevant to the present scenario, namely, (i) gate voltage dependent capacitance, (ii) saturation of the drain current, (iii) the subthreshold slope and (iv) the scaling performance. To gain physical insights into these effects, we also develop a set of semi-analytical equations. The key observations are: (1) A strongly energy-quantized nanowire shows non-monotonic multiple peak C-V characteristics due to discrete contributions from individual subbands; (2) The ballistic drain current saturates better in the UQCL compared to CCL, both in presence and absence of $D_{it}$ and $R_{s,d}$; (3) The subthreshold slope does not suffer any relative degradation in the UQCL compared to CCL, even with $D_{it}$ and $R_{s,d}$; (4) UQCL scaling outperforms CCL in the ideal condition; (5) UQCL scaling is more immune to $R_{s,d}$, but presence of $D_{it}$ and $C_L$ significantly degrades scaling advantages in the UQCL.Comment: Accepted at IEEE Transactions on Electron Device

CCL: a portable and tunable collective communication library for scalable parallel computers

A collective communication library for parallel computers includes frequently used operations such as broadcast, reduce, scatter, gather, concatenate, synchronize, and shift. Such a library provides users with a convenient programming interface, efficient communication operations, and the advantage of portability. A library of this nature, the Collective Communication Library (CCL), intended for the line of scalable parallel computer products by IBM, has been designed. CCL is part of the parallel application programming interface of the recently announced IBM 9076 Scalable POWERparallel System 1 (SP1). In this paper, we examine several issues related to the functionality, correctness, and performance of a portable collective communication library while focusing on three novel aspects in the design and implementation of CCL: 1) the introduction of process groups, 2) the definition of semantics that ensures correctness, and 3) the design of new and tunable algorithms based on a realistic point-to-point communication model

The Impacts of the Climate Change Levy on Manufacturing: Evidence from Microdata

We estimate the impacts of the Climate Change Levy (CCL) on manufacturing plants using panel data from the UK production census. Our identification strategy builds on the comparison of outcomes between plants subject to the CCL and plants that were granted an 80% discount on the levy after joining a Climate Change Agreement (CCA). Exploiting exogenous variation in eligibility for CCA participation, we find that the CCL had a strong negative impact on energy intensity and electricity use. We cannot reject the hypothesis that the tax had no detrimental effects on economic performance and on plant exit.

Cluster-Cluster Lensing and the Case of Abell 383

Extensive surveys of galaxy clusters motivate us to assess the likelihood of cluster-cluster lensing (CCL), namely, gravitational-lensing of a background cluster by a foreground cluster. We briefly describe the characteristics of CCLs in optical, X-ray and SZ measurements, and calculate their predicted numbers for $\Lambda$CDM parameters and a viable range of cluster mass functions and their uncertainties. The predicted number of CCLs in the strong-lensing regime varies from several ($<10$) to as high as a few dozen, depending mainly on whether lensing triaxiality bias is accounted for, through the c-M relation. A much larger number is predicted when taking into account also CCL in the weak-lensing regime. In addition to few previously suggested CCLs, we report a detection of a possible CCL in A383, where background candidate high-$z$ structures are magnified, as seen in deep Subaru observations.Comment: 9 pages, 5 figures, submitted to MNRA