bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving hole injection and carrier distribution in InGaN light-emitting diodes by removing the electron blocking layer and including a unique last quantum barrier
Authors: Cheng Liwen , Chen Haitao , Wu Shudong
Published: August 2015

The effects of removing the AlGaN electron blocking layer (EBL), and using a last quantum barrier (LQB) with a unique design in conventional blue InGaN light-emitting diodes (LEDs), were investigated through simulations. Compared with the conventional LED design that contained a GaN LQB and an AlGaN EBL, the LED that contained an AlGaN LQB with a graded-composition and no EBL exhibited enhanced optical performance and less efficiency droop. This effect was caused by an enhanced electron confinement and hole injection efficiency. Furthermore, when the AlGaN LQB was replaced with a triangular graded-composition, the performance improved further and the efficiency droop was lowered. The simulation results indicated that the enhanced hole injection efficiency and uniform distribution of carriers observed in the quantum wells were caused by the smoothing and thinning of the potential barrier for the holes. This allowed a greater number of holes to tunnel into the quantum wells from the p-type regions in the proposed LED structure.
Two high-field thermodynamically stable conductivity states in photoconductive CdS, one n-type and one p-type
Authors: Böer Karl W.
Published: August 2015

Photoconductive CdS is known to be n-type and develops high-field domains in the range of negative differential conductivities. These domains have been extensively discussed, and when remaining attached to the electrodes have been renamed Böer domains (a broader definition suggested earlier is misleading) [K. Thiessen, Phys. Status Solidi B 248, 2775 (2011)]. They are occurring at high applied voltage in a range at which the current becomes highly non-ohmic that is conventionally described as N-shaped when the conductance decreases with increasing bias or as S-shaped when the current starts to increase again. In this paper only such cases will be discussed in which the current stays below significant Joule heating (no current channel formation), and only for stationary electrode-attached high-field domains. These are the cathode-attached domains that are maintained by field-quenching and are thermodynamically stable. Their finding is summarized in the first segment of this paper. When the applied voltage is increased, an anode-attached hyper-high-field domain develops that is stabilized by a hole blocking anode and will be analyzed in more detail below. It will be shown that they are a thermodynamically stable p-type photoconductive state of CdS. These two new states can be used to determine the carrier densities and mobilities as function of the field and the effective work function in dependence of the spectral distribution of the optical excitation. In a thin slab adjacent to a blocking cathode, the quasi-Fermi levels are spread to a precise amount and are kept there in the entire high-field region. This opens the opportunity to analyze with small modulation of the excitation the trap transition coefficients near these quasi-Fermi levels separately, without broadening interference from other signals. This has already resulted in the discovery of an unusually sharp electron quenching level when the CdS was in a p-type state with an anode adjacent domain. It is also shown that the domains are responsible for the high efficiency of CdTe solar cells when covered with a thin layer of CdS by eliminating junction leakage and increase hole suction into the CdS.
Broadband-antireflective hybrid nanopillar array for photovoltaic application
Authors: Watanabe Keiji , Yamamoto Jiro , Tsuchiya Ryuta
Published: August 2015

Subwavelength structures such as nanopillars, nanoholes, and nanodomes have recently attracted considerable attention as antireflective structures for solar cells. Recent studies on the optical property of nanopillar array revealed that the reflection minimum is related to the diameter, the pitch, and the height of nanopillars. Here, we investigate the “hybrid” nanopillar array, which is composed of different diameters of nanopillars. Finite differential time domain simulations revealed that the photogeneration in a hybrid nanopillar array is spatially heterogeneous: carriers are generated mainly in the narrower pillars for short-wavelength incident light and in the thicker pillars for long-wavelength light, respectively. Hybrid silicon nanopillar arrays fabricated by using electron beam lithography and dry etching show excellent broadband antireflection property. Hybrid nanopillar array is thus highly promising for next-generation antireflection for photovoltaic applications.
High speed intravascular photoacoustic imaging with fast optical parametric oscillator laser at 1.7 μm
Authors: Piao Zhonglie , Ma Teng , Li Jiawen , Wiedmann Maximilian T. , Huang Shenghai , Yu Mingyue , Kirk Shung K. , Zhou Qifa , Kim Chang-Seok , Chen Zhongping
Published: August 2015

Intravascular photoacoustic imaging at 1.7 μm spectral band has shown promising capabilities for lipid-rich vulnerable atherosclerotic plaque detection. In this work, we report a high speed catheter-based integrated intravascular photoacoustic/intravascular ultrasound (IVPA/IVUS) imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A lipid-mimicking phantom and atherosclerotic rabbit abdominal aorta were imaged at 1 frame per second, which is two orders of magnitude faster than previously reported in IVPA imaging with the same wavelength. Clear photoacoustic signals by the absorption of lipid rich deposition demonstrated the ability of the system for high speed vulnerable atherosclerotic plaques detection.
Enhanced performance thermal diode via thermal boundary resistance at nanoscale
Authors: Tovar-Padilla M. , Licea-Jimenez L. , Pérez-Garcia S. A. , Alvarez-Quintana J.
Published: August 2015

Hypothetically, a thermal rectifier is a device which leads a greater heat flux in one direction than another one, similarly as the electrical diode works for the electrical flux. Here, a drastic increment in the rectification factor has been obtained in nanoscale layered thermal diodes due to the effect of thermal boundary resistance present on an asymmetrical stack of nanofilms. Measurements show a thermal rectification factor as large as 3.3 under a temperature bias well below 1 K, which is the biggest thermal rectification factor reported at room temperature compared to previously reported thermal diodes so far. According to the direction of the applied heat flux, the observed impact of the thermal boundary resistance on the device is manifested through the presence of an asymmetric temperature rise along the heat transfer axis. Such effect provides an alternative route for the development of high performance thermal diodes.
A review on bi-source, off-grid hybrid power generation systems based on alternative energy sources
Authors: Aziz Muhammad Shahzad , Saleem Umair , Ali Ehsan , Siddiq Khalid
Published: August 2015

The world will need greatly increased energy supply in coming years because of the rapidly increasing world population and depleting natural resources. For a long time, conventional energy sources have been utilized for power generation, but now it is of great concern that the rapid depletion of conventional sources added with their economic and environmental concerns are incompatible to address issues like growing electricity demand and environmental damages. Utilization of the alternative energy sources is compulsory to minimize the energy crisis around the world. Based on the alternative energy sources, a number of power generation systems have been designed to contribute for the management of optimized energy supply systems. The unpredictable nature of alternative energy sources is their common drawback, and they do not harness usable power for some considerable duration of time over the year. Therefore, trends are in progress to integrate two or more than two of these alternative energy systems to meet the required electricity supply in power generation operations. These systems are designated as hybrid systems and can be grid connected or off-grid depending upon their purpose and mode of fabrication. Off grid hybrid systems are popular for the electrification of the isolated and far-flung areas, where the grid supply is absent. This study mainly focuses on main 10 off grid, bi-source hybrid systems for power generation highlighting their role in energy stability. Systems' hybridization, power generation, energy flow schemes, operation schemes, and storage and backup needs have been addressed thoroughly in this study to provide a handy reference to stake holders for further work in this regime.
Solving probabilistic load flow in smart distribution grids using heuristic methods
Authors: Nikmehr N. , Najafi Ravadanegh S.
Published: August 2015

Uncertainties in smart distribution grids operation are important and challenging issues. The integration of the renewable energy resources (RERs) into the conventional distribution networks changes the radial structure of the network while its inherent characteristics such as high R/X ration of feeders remained unchanged. Conventional power flow methods may be not be suitable or efficient for smart distribution networks. This paper proposes a heuristic optimization based Probabilistic Load Flow (PLF) method to overcome new problems of future distribution networks. The proposed algorithm is suitable for any smart distribution networks with RERs. Imperialist Competitive Algorithm is used to formulate and solve the PLF considering RERs. Comparative studies with small and large sample numbers of RERs and load data are done to evaluate the effect of the samples number on the performance and simulation time. The results are compared with Monte Carlo Simulation (MCS) method. Some network parameters such as buses voltage, feeders power, and network loss in modified 33-bus network are given as Probability Density Function and compared by MCS. Based on the results the proposed algorithm can solve the PLF, regardless of the type of distribution network.
New Cytotoxic Norditerpenes from the Australian Nudibranchs Goniobranchus Splendidus and Goniobranchus Daphne
Authors: Hirayama Yuichiro , Katavic Peter L. , White Andrew M. , Pierens Gregory K. , Lambert Lynette K. , Winters Anne E. , Kigoshi Hideo , Kita Masaki , Garson Mary J.
Published: August 2015

This study reports the isolation and characterisation of six new metabolites with ‘gracilin’-type carbon skeletons and of aplytandiene-3 from the Australian nudibranch Goniobranchus splendidus. The structure of gracilin G is revised, and the C-6 configuration deduced by comparison of calculated 3JC/H values with values measured using the EXSIDE pulse sequence. A lactone isolated from Goniobranchus daphne contains a rearranged spongionellin-type skeleton. Screening of selected metabolites revealed significant cytotoxicity against a HeLa S3 cell line by five of the new terpenes.
Cross-cultural training of general practitioner registrars: how does it happen?
Authors: Watt Kelly , Abbott Penny , Reath Jenny
Published: August 2015

An equitable multicultural society requires general practitioners (GPs) to be proficient in providing health care to patients from diverse backgrounds. GPs are required to have a certain attitudes, knowledge and skills known as cultural competence. Given its importance to registrar training, the aim of this study was to explore ways in which GP registrars are currently developing cultural competence. This study employed a survey design for GP registrars in Western Sydney. Training approaches to cultural competence that are relevant to the Australian General Practice setting include exposure to diversity, attitudes, knowledge and skills development. The 43 GP registrar respondents in Western Sydney are exposed to a culturally diverse patient load during training. Registrars report a variety of teachings related to cross-cultural training, but there is little consistency, with the most common approach entailing listening to patients’ personal stories. Exposure to cultural diversity appears to be an important way in which cultural competency is developed. However, guidance and facilitation of skills development throughout this exposure is required and currently may occur opportunistically rather than consistently.
Assessing capture and tagging methods for brolgas, Antigone rubicunda (Gruidae)
Authors: Veltheim Inka , Chavez-Ramirez Felipe , Hill Richard , Cook Simon
Published: August 2015

Context
Studies assessing welfare issues and efficiency of animal capture methods are important, as capture can pose a significant welfare risk and methods can be time consuming to develop. It is imperative to choose methods that minimise injuries, maximise capture rates and minimise time spent on capture.

Aims
To test methods of crane capture and tagging (transmitter, colour and metal band fitting), and to compare and develop safe and time efficient methods for capturing brolgas (Antigone rubicunda).

Methods
We tested three types of noose traps, cannon nets, clap-nets, spotlighting at night roosts and active pursuit of pre-fledged chicks. We also tested two band sizes and two transmitter attachment methods. We compared the success and capture efficiency of these methods and considered welfare issues by comparing the number of injuries and mortalities resulting from these methods.

Key results
We successfully captured brolgas with noose traps and a cannon net, and by using active pursuit of pre-fledged chicks. Noose traps became more efficient when deployed with call playback and taxidermy decoys. Australian noose traps and active pursuit of pre-fledged chicks were the safest methods with fewest injuries.

Conclusions
For maximum capture success with minimum injuries to target and non-target species, we recommend noose traps with call playback and taxidermy decoys for capturing adult and juvenile brolgas at feeding areas, and active pursuit for pre-fledged chicks at breeding sites. Noose lines should have elastic at both pegged ends, to avoid injuries. To minimise injuries from tagging, we recommend leg-band-fitted transmitters in preference to harness-fitted transmitters, Australian size 35 bands and colour bands with an internal diameter of 22 mm.

Implications
The use of Australian noose traps with call playback and taxidermy decoys is a safe and time efficient method for capturing brolgas, and is also likely to work for other crane species. Our recommendations can help reduce capture-related mortalities and injuries to brolgas (and potentially other cranes), which is crucial, given the brolga is a threatened species.
Mechanical control of mitotic progression in single animal cells
Authors: Cattin Cedric J. , Düggelin Marcel , Martinez-Martin David , Gerber Christoph , Müller Daniel J. , Stewart Martin P.
Published: August 2015

Significance

In animal tissue, most adherent cells round up against confinement to conduct mitosis. Impaired cell rounding is thought to perturb tissue development and homeostasis and contribute to progression of cancer. Due to the lack of suitable experimental tools, however, insight into the mechanical robustness of mitosis in animal cells remains limited. Here we introduce force-feedback–controlled ion beam-sculpted cantilevers to confine single cells and characterize their progression through mitosis. Our approach reveals critical yield forces that trigger cell cortex herniation, loss of F-actin homogeneity, dissipation of intracellular pressure, critical cell-height decrease, mitotic spindle defects, and resultant perturbation of mitotic progression.
Substance Abuse Relapse in Oxford House Recovery Homes: A Survival Analysis Evaluation
Authors: Harvey Ronald , Jason Leonard A. , Ferrari Joseph R.
Published: August 2015

Background

This study used survival analysis to examine risk factors for substance abuse relapse among residents in Oxford Houses (OH), a national network of self-run, self-financed aftercare homes for individuals recovering from substance use disorders.

Methods

Participants who entered OH within 60 days of a 1-year longitudinal study ( N = 268) were selected from of a nationally representative US sample. Discrete-time survival analysis compared baseline risk of relapse with 4 hypothesized survival models that included time-invariant and time-varying factors across 3 subsequent time periods.

Results

The model predicting higher risk for more severe substance use disorders and psychiatric problems was supported. The hypothesized model that predicted time-varying increases in alcohol (but not drug) abstinence self-efficacy significantly affected risk of relapse. Hypothesized demographic and employment variables did not significantly predict relapse risk.

Conclusions

Results suggested that OH recovery homes may reduce relapse by providing closer monitoring and referring additional services to new residents with more severe prior addiction severity. Risk for relapse may also be reduced by enhancing abstinence self-efficacy for alcohol regardless of drug of choice.
Changes in Tear Cytokine Concentrations Following Discontinuation of Soft Contact Lenses—A Pilot Study
Authors: Chao Cecilia , Golebiowski Blanka , Stapleton Fiona , Richdale Kathryn
Published: August 2015

Purpose:

This study investigated changes in selected tear cytokine concentrations (IL-1β, IL-1Ra, IL-6, IL-10, IL-12 (p70), and TNF-α) after a 1-week washout from soft contact lens wear (CLW), and the repeatability of cytokine measurements using custom multiplex assays.

Methods:

A total of 10 subjects completed this 6-visit (immediately following contact lens removal, and after 1, 2, 3, 4, and 7 [±1] days without CLW) pilot study. Approximately 20 to 30 μL of pooled basal tears were collected from both eyes at each visit. Two custom multiplex assays were used by two operators to quantify the concentration of tear cytokines. Tear samples from subjects 1 to 6 were analyzed using the first kit by operator 1. Tear samples from subject 7 to 10 plus additional tear samples from subjects 1 to 5, which were used to determine the between-kit per operator repeatability, were analyzed using the second kit by operator 2. Linear mixed models were used to determine changes in tear cytokine concentrations over time. Between-kit per operator and within-kit per operator repeatabilities were assessed using the Bland and Altman analysis.

Results:

There were no significant changes in tear cytokine concentrations over a 1-week washout of CLW. More than 99% of the tear samples had detectable levels of cytokines using custom multiplex assays. Within-kit per operator repeatability was good, but between-kit per operator repeatability was poor; likely due to protein degradation, differences in operator experience, and operating procedures.

Conclusion:

A washout period may not be necessary when evaluating changes in tear cytokines with new contact lenses or lens care products. A well-trained operator using standardized operating procedures can produce repeatable measurements using custom multiplex assays.
Drug Effects and Clinical Investigations for Contrast-Induced Nephropathy After Coronary Angiography or Percutaneous Coronary Intervention in Patients With Diabetes
Authors: Zhang Man-Man , Lv Qian-Zhou , Li Xiao-Ye
Published: August 2015

The aim of the study was to investigate the risk factors of preprocedural laboratory investigations and drug effects to the incidence of contrast-induced nephropathy (CIN) in patients with diabetes who underwent coronary angiography or percutaneous coronary intervention and to assess the short-term safety. We retrospectively studied a total of 568 patients with diabetes who underwent coronary angiography or percutaneous coronary intervention from January, 2013 to January, 2014 in our hospital and compared the baseline clinical characteristics, especially the laboratory investigations and preprocedural drugs of those 2 groups (with CIN group and without CIN group), and half year follow-up. Overall, 53 (9.33%) patients were developed into CIN according to the definition of an increase of 25% from the baseline of serum creatinine concentration, supposing that on the basis of an increase of 44.2 μmol/L, the incidence would be 0.88% (5/568). No significant differences were found between the 2 groups with respect to age, diabetes mellitus duration, operation type, contrast type and volume, left ventricular ejection fraction, and combined diseases including hypertension, myocardial infarction, Arrhythmia, etc. However, patients with CIN tended to be lighter in body weight (P = 0.027) and were more often female [odds ratio (OR) = 2.8, P < 0.01], and also had a higher prevalence with acute coronary syndrome (OR = 5.1, P < 0.01). On the contrary to most studies, the preprocedural serum creatinine in with CIN group in our study was lower than without CIN group (P < 0.001). As for the preprocedural drugs, statins seemed could decrease the incidence of CIN (OR = 0.34, P < 0.05), and the use of diuretics might increase the occurrence of CIN (OR = 2.62, P < 0.05). As regard to the follow-up results, the hospitalization days and expense of with CIN group were significantly longer and higher than the without CIN group, but no significance was found between rehospitalization rate in half year. Preprocedural preventions are essential because there is no effective treatment for CIN our findings could be considered in clinical practice. There are many risk factors for CIN; it is necessary to distinguish the high-risk patients so as to carry out corresponding protection actions.
The jellyfish buffet: jellyfish enhance seabird foraging opportunities by concentrating prey
Authors: Sato Nobuhiko N. , Kokubun Nobuo , Yamamoto Takashi , Watanuki Yutaka , Kitaysky Alexander S. , Takahashi Akinori
Published: August 2015

High levels of jellyfish biomass have been reported in marine ecosystems around the world, but understanding of their ecological role remains in its infancy. Jellyfish are generally thought to have indirect negative impacts on higher trophic-level predators, through changes in lower trophic pathways. However, high densities of jellyfish in the water column may affect the foraging behaviour of marine predators more directly, and the effects may not always be negative. Here, we present novel observations of a diving seabird, the thick-billed murre, feeding on fish aggregating among the long tentacles of large jellyfish, by using small video loggers attached to the birds. We show that the birds encountered large jellyfish,
Chrysaora melanaster
, during most of their dives, commonly fed on fish associated with jellyfish, and appeared to specifically target jellyfish with a high number of fish aggregating in their tentacles, suggesting the use of jellyfish may provide significant energetic benefits to foraging murres. We conclude that jellyfish provide feeding opportunities for diving seabirds by concentrating forage fish, and that the impacts of jellyfish on marine ecosystems are more complex than previously anticipated and may be beneficial to seabirds.
John Rodney Quayle. 18 November 1926 — 26 February 2006
Authors: Anthony Christopher
Published: August 2015

J. Rodney Quayle was an outstanding microbial biochemist whose early training in pure chemistry was coupled with rigorous enzymology and experience in the relatively new techniques of using radioactive
14
C compounds in the study of metabolic pathways. These he used to investigate and elucidate the pathways of carbon assimilation during microbial growth on compounds with a single carbon atom such as methane and methanol. When he started, little was known about these organisms (methylotrophs), which, largely as a result of his own work and the work inspired by him, have formed the subject of regular international symposia over a period of more than 40 years. After a short time working in Melvin Calvin’s laboratory in California and a very fruitful period in Hans Krebs’s Unit for Research in Cell Metabolism in the University of Oxford he moved for the next 20 years to the University of Sheffield, after which he became a highly successful and popular Vice-Chancellor at the University of Bath. His rigorous approach to his subject, his generosity and inspiration made him a much revered and much loved father figure to generations of microbial biochemists.
Struther Arnott. 25 September 1934 — 20 April 2013
Authors: Rees Sir Dai
Published: August 2015

Struther Arnott worked tirelessly as a researcher, teacher, leader and maker and implementer of policy in universities in Britain and the USA, always carrying his colleagues along with him through his infectious energy and breadth of academic enthusiasms and values. His outlook was shaped by the stimulus of a broad Scottish education that launched wide interests inside and outside science, including the history and literature of classical civilizations. His early research, with John Monteath Robertson FRS, was into structure determination by X-ray diffraction methods for single crystals, at a time when the full power of computers was just becoming realized for solution of the phase problem. With tenacity and originality, he then extended these approaches to materials that were to a greater or lesser extent disordered and even more difficult to solve because their diffraction patterns were poorer in information content. He brought many problems to definitive and detailed conclusion in a field that had been notable for solutions that were partial or vague, especially with oriented fibres of DNA and RNA but also various polysaccharides and synthetic polymers. His first approach was to use molecular model building in combination with difference Fourier analysis. This was followed later, and to even greater effect, by a computer refinement method that he developed himself and called linkedatom least-squares refinement. This has now been adopted as the standard approach by most serious centres of fibre diffraction analysis throughout the world. After the 10 years in which he consolidated his initial reputation at the Medical Research Council Biophysics Unit at King's College, London, in association with Maurice Wilkins FRS, he moved to Purdue University in the USA, first as Professor of Biology then becoming successively Head of the Department of Biological Sciences and Vice-President for Research and Dean of the Graduate School. As well as continuing his research, he contributed to the transformation of biological sciences at that university and to the development of the university's general management. He finally returned to his roots in Scotland as Principal and Vice-Chancellor of the University of St Andrews, to draw on his now formidable experience of international scholarship and institutional management, to reshape the patterns of academic life and mission to sit more happily and successfully within an environment that had become beset with conflict and change. He achieved this without disturbance to the harmony and wisdom embodied in the venerable traditions of that ancient Scottish yet cosmopolitan university.
Magnetic targeting of microbubbles against physiologically relevant flow conditions
Authors: Owen Joshua , Rademeyer Paul , Chung Daniel , Cheng Qian , Holroyd David , Coussios Constantin , Friend Peter , Pankhurst Quentin A. , Stride Eleanor
Published: August 2015

The localization of microbubbles to a treatment site has been shown to be essential to their effectiveness in therapeutic applications such as targeted drug delivery and gene therapy. A variety of different strategies for achieving localization has been investigated, including biochemical targeting, acoustic radiation force, and the incorporation of superparamagnetic nanoparticles into microbubbles to enable their manipulation using an externally applied magnetic field. The third of these strategies has the advantage of concentrating microbubbles in a target region without exposing them to ultrasound, and can be used in conjunction with biochemical targeting to achieve greater specificity. Magnetic microbubbles have been shown to be effective for therapeutic delivery
in vitro
and
in vivo
. Whether this technique can be successfully applied in humans however remains an open question. The aim of this study was to determine the range of flow conditions under which targeting could be achieved.
In vitro
results indicate that magnetic microbubbles can be retained using clinically acceptable magnetic fields, for both the high shear rates (approx. 10
4
s
−1
) found in human arterioles and capillaries, and the high flow rates (approx. 3.5 ml s
−1
) of human arteries. The potential for human
in vivo
microbubble retention was further demonstrated using a perfused porcine liver model.
Towards numerical prediction of cavitation erosion
Authors: Fivel Marc , Franc Jean-Pierre , Chandra Roy Samir
Published: August 2015

This paper is intended to provide a potential basis for a numerical prediction of cavitation erosion damage. The proposed method can be divided into two steps. The first step consists in determining the loading conditions due to cavitation bubble collapses. It is shown that individual pits observed on highly polished metallic samples exposed to cavitation for a relatively small time can be considered as the signature of bubble collapse. By combining pitting tests with an inverse finite-element modelling (FEM) of the material response to a representative impact load, loading conditions can be derived for each individual bubble collapse in terms of stress amplitude (in gigapascals) and radial extent (in micrometres). This step requires characterizing as accurately as possible the properties of the material exposed to cavitation. This characterization should include the effect of strain rate, which is known to be high in cavitation erosion (typically of the order of several thousands s
−1
). Nanoindentation techniques as well as compressive tests at high strain rate using, for example, a split Hopkinson pressure bar test system may be used. The second step consists in developing an FEM approach to simulate the material response to the repetitive impact loads determined in step 1. This includes a detailed analysis of the hardening process (isotropic versus kinematic) in order to properly account for fatigue as well as the development of a suitable model of material damage and failure to account for mass loss. Although the whole method is not yet fully operational, promising results are presented that show that such a numerical method might be, in the long term, an alternative to correlative techniques used so far for cavitation erosion prediction.
Bubble dynamics in a compressible liquid in contact with a rigid boundary
Authors: Wang Qianxi , Liu Wenke , Zhang A. M. , Sui Yi
Published: August 2015

A bubble initiated near a rigid boundary may be almost in contact with the boundary because of its expansion and migration to the boundary, where a thin layer of water forms between the bubble and the boundary thereafter. This phenomenon is modelled using the weakly compressible theory coupled with the boundary integral method. The wall effects are modelled using the imaging method. The numerical instabilities caused by the near contact of the bubble surface with the boundary are handled by removing a thin layer of water between them and joining the bubble surface with its image to the boundary. Our computations correlate well with experiments for both the first and second cycles of oscillation. The time history of the energy of a bubble system follows a step function, reducing rapidly and significantly because of emission of shock waves at inception of a bubble and at the end of collapse but remaining approximately constant for the rest of the time. The bubble starts being in near contact with the boundary during the first cycle of oscillation when the dimensionless stand-off distanceγ=s/Rm< 1, wheresis the distance of the initial bubble centre from the boundary andRmis the maximum bubble radius. This leads to (i) the direct impact of a high-speed liquid jet on the boundary once it penetrates through the bubble, (ii) the direct contact of the bubble at high temperature and high pressure with the boundary, and (iii) the direct impingement of shock waves on the boundary once emitted. These phenomena have clear potential to damage the boundary, which are believed to be part of the mechanisms of cavitation damage.
Arachnid aloft: directed aerial descent in neotropical canopy spiders
Authors: Yanoviak Stephen P. , Munk Yonatan , Dudley Robert
Published: August 2015

The behaviour of directed aerial descent has been described for numerous taxa of wingless hexapods as they fall from the tropical rainforest canopy, but is not known in other terrestrial arthropods. Here, we describe similar controlled aerial behaviours for large arboreal spiders in the genus
Selenops
(Selenopidae). We dropped 59 such spiders from either canopy platforms or tree crowns in Panama and Peru; the majority (93%) directed their aerial trajectories towards and then landed upon nearby tree trunks. Following initial dorsoventral righting when necessary, falling spiders oriented themselves and then translated head-first towards targets; directional changes were correlated with bilaterally asymmetric motions of the anterolaterally extended forelegs. Aerial performance (i.e. the glide index) decreased with increasing body mass and wing loading, but not with projected surface area of the spider. Along with the occurrence of directed aerial descent in ants, jumping bristletails, and other wingless hexapods, this discovery of targeted gliding in selenopid spiders further indicates strong selective pressures against uncontrolled falls into the understory for arboreal taxa.
Adaptation mechanism of interlimb coordination in human split-belt treadmill walking through learning of foot contact timing: a robotics study
Authors: Fujiki Soichiro , Aoi Shinya , Funato Tetsuro , Tomita Nozomi , Senda Kei , Tsuchiya Kazuo
Published: August 2015

Human walking behaviour adaptation strategies have previously been examined using split-belt treadmills, which have two parallel independently controlled belts. In such human split-belt treadmill walking, two types of adaptations have been identified: early and late. Early-type adaptations appear as rapid changes in interlimb and intralimb coordination activities when the belt speeds of the treadmill change between tied (same speed for both belts) and split-belt (different speeds for each belt) configurations. By contrast, late-type adaptations occur after the early-type adaptations as a gradual change and only involve interlimb coordination. Furthermore, interlimb coordination shows after-effects that are related to these adaptations. It has been suggested that these adaptations are governed primarily by the spinal cord and cerebellum, but the underlying mechanism remains unclear. Because various physiological findings suggest that foot contact timing is crucial to adaptive locomotion, this paper reports on the development of a two-layered control model for walking composed of spinal and cerebellar models, and on its use as the focus of our control model. The spinal model generates rhythmic motor commands using an oscillator network based on a central pattern generator and modulates the commands formulated in immediate response to foot contact, while the cerebellar model modifies motor commands through learning based on error information related to differences between the predicted and actual foot contact timings of each leg. We investigated adaptive behaviour and its mechanism by split-belt treadmill walking experiments using both computer simulations and an experimental bipedal robot. Our results showed that the robot exhibited rapid changes in interlimb and intralimb coordination that were similar to the early-type adaptations observed in humans. In addition, despite the lack of direct interlimb coordination control, gradual changes and after-effects in the interlimb coordination appeared in a manner that was similar to the late-type adaptations and after-effects observed in humans. The adaptation results of the robot were then evaluated in comparison with human split-belt treadmill walking, and the adaptation mechanism was clarified from a dynamic viewpoint.
Compartmentalization of membrane trafficking, glucose transport, glycolysis, actin, tubulin and the proteasome in the cytoplasmic droplet/Hermes body of epididymal sperm
Authors: Au Catherine E. , Hermo Louis , Byrne Elliot , Smirle Jeffrey , Fazel Ali , Kearney Robert E. , Smith Charles E. , Vali Hojatollah , Fernandez-Rodriguez Julia , Simon Paul H. G. , Mandato Craig , Nilsson Tommy , Bergeron John J. M.
Published: August 2015

Discovered in 1909 by Retzius and described mainly by morphology, the cytoplasmic droplet of sperm (renamed here the Hermes body) is conserved among all mammalian species but largely undefined at the molecular level. Tandem mass spectrometry of the isolated Hermes body from rat epididymal sperm characterized 1511 proteins, 43 of which were localized to the structurein situby light microscopy and two by quantitative electron microscopy localization. Glucose transporter 3 (GLUT-3) glycolytic enzymes, selected membrane traffic and cytoskeletal proteins were highly abundant and concentrated in the Hermes body. By electron microscope gold antibody labelling, the Golgi trafficking protein TMED7/p27 localized to unstacked flattened cisternae of the Hermes body, as did GLUT-3, the most abundant protein. Its biogenesis was deduced through the mapping of protein expression for all 43 proteins during male germ cell differentiation in the testis. It is at the terminal step 19 of spermiogenesis that the 43 characteristic proteins accumulated in the nascent Hermes body.
Social dominance modulates eavesdropping in zebrafish
Authors: Abril-de-Abreu Rodrigo , Cruz Ana S. , Oliveira Rui F.
Published: August 2015

Group living animals may eavesdrop on signalling interactions between conspecifics and integrate it with their own past social experience in order to optimize the use of relevant information from others. However, little is known about this interplay between public (eavesdropped) and private social information. To investigate it, we first manipulated the dominance status of bystander zebrafish. Next, we either allowed or prevented bystanders from observing a fight. Finally, we assessed their behaviour towards the winners and losers of the interaction, using a custom-made video-tracking system and directional analysis. We found that only dominant bystanders who had seen the fight revealed a significant increase in directional focus (a measure of attention) towards the losers of the fights. Furthermore, our results indicate that information about the fighters' acquired status was collected from the signalling interaction itself and not from post-interaction status cues, which implies the existence of individual recognition in zebrafish. Thus, we show for the first time that zebrafish, a highly social model organism, eavesdrop on conspecific agonistic interactions and that this process is modulated by the eavesdroppers' dominance status. We suggest that this type of integration of public and private information may be ubiquitous in social learning processes.
Object localization using a biosonar beam: how opening your mouth improves localization
Authors: Arditi G. , Weiss A. J. , Yovel Y.
Published: August 2015

Determining the location of a sound source is crucial for survival. Both predators and prey usually produce sound while moving, revealing valuable information about their presence and location. Animals have thus evolved morphological and neural adaptations allowing precise sound localization. Mammals rely on the temporal and amplitude differences between the sound signals arriving at their two ears, as well as on the spectral cues available in the signal arriving at a single ear to localize a sound source. Most mammals rely on passive hearing and are thus limited by the acoustic characteristics of the emitted sound. Echolocating bats emit sound to perceive their environment. They can, therefore, affect the frequency spectrum of the echoes they must localize. The biosonar sound beam of a bat is directional, spreading different frequencies into different directions. Here, we analyse mathematically the spatial information that is provided by the beam and could be used to improve sound localization. We hypothesize how bats could improve sound localization by altering their echolocation signal design or by increasing their mouth gape (the size of the sound emitter) as they, indeed, do in nature. Finally, we also reveal a trade-off according to which increasing the echolocation signal's frequency improves the accuracy of sound localization but might result in undesired large localization errors under low signal-to-noise ratio conditions.
Enabling quaternion derivatives: the generalized HR calculus
Authors: Xu Dongpo , Jahanchahi Cyrus , Took Clive C. , Mandic Danilo P.
Published: August 2015

Quaternion derivatives exist only for a very restricted class of analytic (regular) functions; however, in many applications, functions of interest are real-valued and hence not analytic, a typical case being the standard real mean square error objective function. The recent HR calculus is a step forward and provides a way to calculate derivatives and gradients of both analytic and non-analytic functions of quaternion variables; however, the HR calculus can become cumbersome in complex optimization problems due to the lack of rigorous product and chain rules, a consequence of the non-commutativity of quaternion algebra. To address this issue, we introduce the generalized HR (GHR) derivatives which employ quaternion rotations in a general orthogonal system and provide the left- and right-hand versions of the quaternion derivative of general functions. The GHR calculus also solves the long-standing problems of product and chain rules, mean-value theorem and Taylor's theorem in the quaternion field. At the core of the proposed GHR calculus is quaternion rotation, which makes it possible to extend the principle to other functional calculi in non-commutative settings. Examples in statistical learning theory and adaptive signal processing support the analysis.
Rapid eco-evolutionary responses in perturbed phytoplankton communities
Authors: Thibodeau Geneviève , Walsh David A. , Beisner Beatrix E.
Published: August 2015

Biodiversity currently faces unprecedented threats owing to species extinctions. Ecologically, compensatory dynamics can ensure stable community biomass following perturbation. However, whether there is a contribution of genetic diversity to community responses is an outstanding question. To date, the contribution of evolutionary processes through genotype shifts has not been assessed in naturally co-occurring multi-species communities in the field. We examined the mechanisms contributing to the response of a lake phytoplankton community exposed to either a press or pulse acidification perturbation in lake mesocosms. To assess community shifts in the ecological response of morphospecies, we identified taxa microscopically. We also assessed genotype shifts by sequencing the ITS2 region of ribosomal DNA. We observed ecological and genetic contributions to community responses. The ecological response was attributed to compensatory morphospecies dynamics and occurred primarily in the Pulse perturbation treatment. In the Press treatments, in addition to compensatory dynamics, we observed evidence for genotype selection in two species of chlorophytes,
Desmodesmus cuneatus
and an unidentified
Chlamydomonas
. Our study demonstrates that while genotype selection may be rare, it is detectable and occurs especially when new environmental conditions are maintained for long enough to force selection processes on standing variation.
Orchid phylogenomics and multiple drivers of their extraordinary diversification
Authors: Givnish Thomas J. , Spalink Daniel , Ames Mercedes , Lyon Stephanie P. , Hunter Steven J. , Zuluaga Alejandro , Iles William J. D. , Clements Mark A. , Arroyo Mary T. K. , Leebens-Mack James , Endara Lorena , Kriebel Ricardo , Neubig Kurt M. , Whitten W. Mark , Williams Norris H. , Cameron Kenneth M.
Published: August 2015

Orchids are the most diverse family of angiosperms, with over 25 000 species, more than mammals, birds and reptiles combined. Tests of hypotheses to account for such diversity have been stymied by the lack of a fully resolved broad-scale phylogeny. Here, we provide such a phylogeny, based on 75 chloroplast genes for 39 species representing all orchid subfamilies and 16 of 17 tribes, time-calibrated against 17 angiosperm fossils. A supermatrix analysis places an additional 144 species based on three plastid genes. Orchids appear to have arisen roughly 112 million years ago (Mya); the subfamilies Orchidoideae and Epidendroideae diverged from each other at the end of the Cretaceous; and the eight tribes and three previously unplaced subtribes of the upper epidendroids diverged rapidly from each other between 37.9 and 30.8 Mya. Orchids appear to have undergone one significant acceleration of net species diversification in the orchidoids, and two accelerations and one deceleration in the upper epidendroids. Consistent with theory, such accelerations were correlated with the evolution of pollinia, the epiphytic habit, CAM photosynthesis, tropical distribution (especially in extensive cordilleras), and pollination via Lepidoptera or euglossine bees. Deceit pollination appears to have elevated the number of orchid species by one-half but not via acceleration of the rate of net diversification. The highest rate of net species diversification within the orchids (0.382 sp sp
−1
My
−1
) is 6.8 times that at the Asparagales crown.
Envelope gene sequences encoding variable regions 3 and 4 are involved in macrophage tropism of feline immunodeficiency virus
Authors: Vahlenkamp Thomas W. , De Ronde Anthony , Schuurman Nancy N. M. P. , van Vliet Arno L. W. , van Drunen Judith , Horzinek Marian C. , Egberink Herman F.
Published: August 2015

The envelope is of cardinal importance for the entry of feline immunodeficiency virus (FIV) into its host cells, which consist of cells of the immune system including macrophages. To characterize the envelope glycoprotein determinants involved in macrophage tropism, chimeric infectious molecular clones were constructed containing envelope gene sequences from isolates that had been propagated in peripheral blood mononuclear cells (PBMC). The progeny virus was examined for growth in PBMC and bone marrow-derived macrophages and viruses with different replication kinetics in macrophages were selected. Envelope-chimeric viruses revealed that nucleotide sequences encoding variable regions 3 and 4 of the surface glycoprotein, SU, are involved in macrophage tropism of FIV. To assess the biological importance of this finding, the phenotypes of envelope proteins of viruses derived from bone marrow, brain, lymph node and PBMC of an experimentally FIV-infected, healthy cat were examined. Since selection during propagation had to be avoided, provirus envelope gene sequences were amplified directly and cloned into an infectious molecular clone of FIV strain Petaluma. The viruses obtained were examined for their replication properties. Of 15 clones tested, 13 clones replicated both in PBMC and macrophages, two (brain-derived clones) replicated in PBMC only and none replicated in Crandell feline kidney cells or astrocytes. These results indicate that dual tropism for PBMC and macrophages is a common feature of FIV variants present in vivo.