Anatomic-electrophysiological correlations concerning the pathways for atrioventricular conduction.

The remarkable success of radiofrequency ablation in recent decades in curing atrioventricular nodal reentrant tachycardias has intensified efforts to provide a solid theoretical basis for understanding the mechanisms of atrioventricular transmission. These efforts, which were made by both anatomists and electrophysiologists, frequently resulted in seemingly controversial observations. Quantitatively and qualitatively, our understanding of the mysteries of propagation through the inhomogeneous and extremely complex atrioventricular conduction axis is much deeper than it was at the beginning of the past century. We must go back to the initial sources, nonetheless, in an attempt to provide a common ground for evaluating the morphological and electrophysiological principles of junctional arrhythmias. In this review, we provide an account of the initial descriptions, which still provide an appropriate foundation for interpreting recent electrophysiological findings

An experimental investigation of turbulent forced convection heat transfer by a multi-walled carbon-nanotube nanofluid

Abstract In this work, a nanofluid based on multi-walled carbon nanotubes was formulated, and its heat transfer characteristics experimentally examined for turbulent flow in a straight tube. The experiments found that using the nanofluid resulted in an increase in pumping power and also a decrease in the observed convective heat transfer characteristics. This suggests that multi-walled carbon nanotube nanofluids in turbulent flows will actually impair heat transfer rather than improve it, and so may not be an appropriate heat transfer media in forced turbulent flows

The Impact of the Parabolic Dish Concentrator on the Wind Induced Heat Loss From Its Receiver

Abstract To achieve higher operating temperatures, power output and system efficiencies in parabolic dish cavity receivers, larger dish sizes and structures are used to increase the concentration ratio. This increases capital investment and installation costs, which in turn places a much stronger emphasis on accurately predicting the performance of the system and the heat loss from it. Numerous studies have investigated the natural convection heat losses from cavity receivers, and some have examined a cavity exposed to wind. However, the effect of the dish on the wind flow and subsequently the heat loss from the receiver has not been widely considered. In this work, computational fluid dynamics was used to model the flow of air around a parabolic dish concentrator operating at varying angles of operation. The flow fields were validated using wind tunnel testing and published data regarding the aerodynamic characteristics of parabolic dishes. The results showed that the orientation of the dish has a significant effect on the flow structure near the receiver. Subsequently, using the validated method, the convective heat loss from the receiver of a large parabolic dish system was determined for a range of operating conditions. The results support the assertion that the flow characteristics near the cavity receiver aperture depend strongly on the orientation of the dish structure. This resulted in the calculated heat loss being up to 40% lower than previous studies where the presence of the dish was included. As such, the wind flow around the dish needs to be accounted for when analyzing the performance of parabolic dish systems to avoid an overly conservative and hence more expensive design

Optimal sizing of a wind-photovoltaic-battery hybrid renewable energy system considering socio-demographic factors

The sizing of a stand-alone wind-photovoltaic-battery hybrid renewable energy system (HRES) is greatly influenced by socio-demographic factors however, few studies have examined how socio-demographic factors, as borne out by different electrical usage patterns, influence the size of HRESs. This paper investigates how these factors influence the optimal sizing of a stand-alone HRES using a hybrid optimization method to match the available renewable energy with the demand. In this regard, different energy usage patterns resulting from users socio-demographic profile have been investigated and used for the optimal sizing of a HRES. The results show that the electricity usage profile of a site has a significant impact on the sizing and design of the system. Further, the results illustrate that one can design a system that meets the demand profiles resulting from socio-demographic factors with a minimum unmet load; however, by optimizing systems to the users socio-demographic profile, significant cost savings can be made

Performance of a V-trough photovoltaic/thermal concentrator

The idea of concentrating solar energy to increase the output of photovoltaic and solar thermal collectors is an area that has received significant attention. In this study, a design model for a V-trough concentrating photovoltaic/thermal solar collector was theoretically analysed and validated with experimental data. The results showed that the V-trough offered improved electrical yields from both concentrating radiation onto the photovoltaic cells and also by actively cooling them. Also, it was shown that the V-trough could be made of a durable (long life) stainless steel, rather than the more reflective aluminium, while still offering a 25% increase in incident radiation over a typical year. However it was noted that modifications would be needed to improve cooling and to increase the thermal efficiency by reducing heat losses

Studies of control strategies for building integrated solar energy system

Research and development work on Building Integrated Solar Energy Systems (BISES) has become an area of growing interest, not only in New Zealand (NZ) but worldwide. This interest has led to a significant growth in the use of solar energy to provide heating and electricity generation. This paper presents the theoretical and experimental results of a novel building integrated solar hot water system developed using commercial long run roofing materials. This work shows that it is possible to achieve effective integration that maintains the aesthetics of the building and also provides useful thermal energy. The results of a 6.73m2 glazed domestic hot water systems are presented. The key design parameters of the Building Integrated Thermal (BIT) system were identified and implemented in a TRansient SYstem Simulation (TRNSYS) model. Validation results comparing the simulation in TRNSYS and real experimentation show that experimental and simulation responses are close to each other. The coupling of TRNSYS and Matlab/Simulink shows the possibility to use Matlab/Simulink for developing appropriate control strategies for BIT roofing systems. Preliminary Fuzzy Logic (FL) intelligent controller was implemented in a Fuzzy Integrated System (FIS) toolbox in a Matlab/Simulink model and linked into TRNSYS model. Further work is needed to identify and design advanced predictive control strategies for the Building Integrated Photovoltaic Thermal (BIPVT) solar system and determine how the performance can be optimized

Sirtuin 5 depletion impairs mitochondrial function in human proximal tubular epithelial cells

Ischemia is a major cause of kidney damage. Proximal tubular epithelial cells (PTECs) are highly susceptible to ischemic insults that frequently cause acute kidney injury (AKI), a potentially life-threatening condition with high mortality. Accumulating evidence has identified altered mitochondrial function as a central pathologic feature of AKI. The mitochondrial NAD+-dependent enzyme sirtuin 5 (SIRT5) is a key regulator of mitochondrial form and function, but its role in ischemic renal injury (IRI) is unknown. SIRT5 expression was increased in murine PTECs after IRI in vivo and in human PTECs (hPTECs) exposed to an oxygen/nutrient deprivation (OND) model of IRI in vitro. SIRT5-depletion impaired ATP production, reduced mitochondrial membrane potential, and provoked mitochondrial fragmentation in hPTECs. Moreover, SIRT5 RNAi exacerbated OND-induced mitochondrial bioenergetic dysfunction and swelling, and increased degradation by mitophagy. These findings suggest SIRT5 is required for normal mitochondrial function in hPTECs and indicate a potentially important role for the enzyme in the regulation of mitochondrial biology in ischemia

Direct Observation of the Superfluid Phase Transition in Ultracold Fermi Gases

Water freezes into ice, atomic spins spontaneously align in a magnet, liquid helium becomes superfluid: Phase transitions are dramatic phenomena. However, despite the drastic change in the system's behaviour, observing the transition can sometimes be subtle. The hallmark of Bose-Einstein condensation (BEC) and superfluidity in trapped, weakly interacting Bose gases is the sudden appearance of a dense central core inside a thermal cloud. In strongly interacting gases, such as the recently observed fermionic superfluids, this clear separation between the superfluid and the normal parts of the cloud is no longer given. Condensates of fermion pairs could be detected only using magnetic field sweeps into the weakly interacting regime. The quantitative description of these sweeps presents a major theoretical challenge. Here we demonstrate that the superfluid phase transition can be directly observed by sudden changes in the shape of the clouds, in complete analogy to the case of weakly interacting Bose gases. By preparing unequal mixtures of the two spin components involved in the pairing, we greatly enhance the contrast between the superfluid core and the normal component. Furthermore, the non-interacting wings of excess atoms serve as a direct and reliable thermometer. Even in the normal state, strong interactions significantly deform the density profile of the majority spin component. We show that it is these interactions which drive the normal-to-superfluid transition at the critical population imbalance of 70(5)%.Comment: 16 pages (incl. Supplemental Material), 5 figure

Release of Lungworm Larvae from Snails in the Environment: Potential for Alternative Transmission Pathways

Background: Gastropod-borne parasites may cause debilitating clinical conditions in animals and humans following the consumption of infected intermediate or paratenic hosts. However, the ingestion of fresh vegetables contaminated by snail mucus and/or water has also been proposed as a source of the infection for some zoonotic metastrongyloids (e.g., Angiostrongylus cantonensis). In the meantime, the feline lungworms Aelurostrongylus abstrusus and Troglostrongylus brevior are increasingly spreading among cat populations, along with their gastropod intermediate hosts. The aim of this study was to assess the potential of alternative transmission pathways for A. abstrusus and T. brevior L3 via the mucus of infected Helix aspersa snails and the water where gastropods died. In addition, the histological examination of snail specimens provided information on the larval localization and inflammatory reactions in the intermediate host. Methodology/Principal Findings: Twenty-four specimens of H. aspersa received ~500 L1 of A. abstrusus and T. brevior, and were assigned to six study groups. Snails were subjected to different mechanical and chemical stimuli throughout 20 days in order to elicit the production of mucus. At the end of the study, gastropods were submerged in tap water and the sediment was observed for lungworm larvae for three consecutive days. Finally, snails were artificially digested and recovered larvae were counted and morphologically and molecularly identified. The anatomical localization of A. abstrusus and T. brevior larvae within snail tissues was investigated by histology. L3 were detected in the snail mucus (i.e., 37 A. abstrusus and 19 T. brevior) and in the sediment of submerged specimens (172 A. abstrusus and 39 T. brevior). Following the artificial digestion of H. aspersa snails, a mean number of 127.8 A. abstrusus and 60.3 T. brevior larvae were recovered. The number of snail sections positive for A. abstrusus was higher than those for T. brevior. Conclusions: Results of this study indicate that A. abstrusus and T. brevior infective L3 are shed in the mucus of H. aspersa or in water where infected gastropods had died submerged. Both elimination pathways may represent alternative route(s) of environmental contamination and source of the infection for these nematodes under field conditions and may significantly affect the epidemiology of feline lungworms. Considering that snails may act as intermediate hosts for other metastrongyloid species, the environmental contamination by mucus-released larvae is discussed in a broader context

Cellulose acetate phthalate, a common pharmaceutical excipient, inactivates HIV-1 and blocks the coreceptor binding site on the virus envelope glycoprotein gp120

BACKGROUND: Cellulose acetate phthalate (CAP), a pharmaceutical excipient used for enteric film coating of capsules and tablets, was shown to inhibit infection by the human immunodeficiency virus type 1 (HIV-1) and several herpesviruses. CAP formulations inactivated HIV-1, herpesvirus types 1 (HSV-1) and 2 (HSV-2) and the major nonviral sexually transmitted disease (STD) pathogens and were effective in animal models for vaginal infection by HSV-2 and simian immunodeficiency virus. METHODS: Enzyme-linked immunoassays and flow cytometry were used to demonstrate CAP binding to HIV-1 and to define the binding site on the virus envelope. RESULTS: 1) CAP binds to HIV-1 virus particles and to the envelope glycoprotein gp120; 2) this leads to blockade of the gp120 V3 loop and other gp120 sites resulting in diminished reactivity with HIV-1 coreceptors CXCR4 and CCR5; 3) CAP binding to HIV-1 virions impairs their infectivity; 4) these findings apply to both HIV-1 IIIB, an X4 virus, and HIV-1 BaL, an R5 virus. CONCLUSIONS: These results provide support for consideration of CAP as a topical microbicide of choice for prevention of STDs, including HIV-1 infection