2015 David Cushing Prize

The prize honors the memory of David Cushing, Founding Editor of Journal of Plankton Research. It is awarded annually for the best paper by an early career stage scientist published in the journal during the previous year. The prize helps foster the interesting and high-quality papers by young scientists that David Cushing so actively supported. The 2015 David Cushing Prize has been awarded to Bingzhang Chen for his paper, “Patterns of thermal limits of phytoplankton” (J. Plankton Res. 37, 285–292) Bingzhang Chen obtained his PhD with a major in Marine Environmental Science at the Hong Kong University of Science and Technology under the supervision of Dr Hongbin Liu in 2008. He also worked with Dr Zoe Finkel and Dr Andrew Irwin in Mount Allison University, Canada, from 2009 to 2010. During this time, he started to learn the R language and entered the field of data analysis and programming. This experience has been proved very useful for his later work.

Expanded iron uta spectra - Probing the thermal stability limits in AGN clouds

The Fe unresolved transition arrays (UTAs) produce prominent features in the 15-17 Å wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration. © 2013. The American Astronomical Society. All rights reserved.

Loss of thermal refugia near equatorial range limits

This study examines the importance of thermal refugia along the majority of the geographical range of a key inter- tidal species (Patella vulgata Linnaeus, 1758) on the Atlantic coast of Europe. We asked whether differences between sun-exposed and shaded microhabitats were responsible for differences in physiological stress and ecological perfor- mance and examined the availability of refugia near equatorial range limits. Thermal differences between sun- exposed and shaded microhabitats are consistently associated with differences in physiological performance, and the frequency of occurrence of high temperatures is most probably limiting the maximum population densities sup- ported at any given place. Topographical complexity provides thermal refugia throughout most of the distribution range, although towards the equatorial edges the magnitude of the amelioration provided by shaded microhabitats is largely reduced. Importantly, the limiting effects of temperature, rather than being related to latitude, seem to be tightly associated with microsite variability, which therefore is likely to have profound effects on the way local popu- lations (and consequently species) respond to climatic changes.

Piezoelectric PVDF materials performance and operation limits in space environments

Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture space-based telescopes. Dimensional adjustments of adaptive polymer films are achieved via charge deposition and require a detailed understanding of the piezoelectric material responses which are expected to suffer due to strong vacuum UV, gamma, X-ray, energetic particles and atomic oxygen under low earth orbit exposure conditions. The degradation of PVDF and its copolymers under various stress environments has been investigated. Initial radiation aging studies using gamma- and e-beam irradiation have shown complex material changes with significant crosslinking, lowered melting and Curie points (where observable), effects on crystallinity, but little influence on overall piezoelectric properties. Surprisingly, complex aging processes have also been observed in elevated temperature environments with annealing phenomena and cyclic stresses resulting in thermal depoling of domains. Overall materials performance appears to be governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and AO exposure is evident as depoling and surface erosion. Major differences between individual copolymers have been observed providing feedback on material selection strategies.

Theoretical Maximum Limits on Power-Handling Capacity of HVDC Cables

In the case of an ac cable, power transmission is limited by the length of the cable due to the capacitive reactive current component. It is well known that high-voltage direct current (HVDC) cables do not have such limitations. However, insulation-related thermal problems pose a limitation on the power capability of HVDC cables. The author presents a viable theoretical development, a logical extension to Whitehead's theory on thermal limitations of the insulation. The computation of the maximum power-carrying capability of HVDC cables subject to limits on the maximum operable temperature of the insulation is presented. The limitation on the power-carrying capability is closely associated with the electrothermal insulation failure. The effect of environmental interaction by way of external thermal resistance, an important aspect, is also considered in the formulations. The Lagrange multiplier method has been used to handle the ensuing optimization problem. The theory is based on an accepted theory of thermal breakdown in insulation and is an important and a coherent extension of great significance.

Thermal Management of Electronics Using PCM-Based Heat Sink Subjected to Cyclic Heat Load

Designing a heat sink based on a phase change material (PCM) under cyclic loading is a critical issue. For cyclic operation, it is required that the fraction of the PCM melting during the heating cycle should completely resolidify during the cooling period, so that that thermal storage unit can be operated for an unlimited number of cycles. Accordingly, studies are carried out to find the parameters influencing the behavior of a PCM under cyclic loading. A number of parameters are identified in the process, the most important ones being the duty cycle and heat transfer coefficient (h) for cooling. The required h or the required cooling period for complete resolidification for infinite cyclic operation of a conventional PCM-based heat sink is found to be very high and unrealistic with air cooling from the surface. To overcome this problem, the conventional design is modified where h and the area exposed to heat transfer can be independently controlled. With this arrangement, the enhanced area provided for cooling keeps h within realistic limits. Analytical investigation is carried out to evaluate the thermal performance of this modified PCM-based heat sink in comparison to those with conventional designs. Experiments are also performed on both the conventional and the modified PCM-based heat sinks to validate the new findings.

Exploring novel methods to achieve sensitivity limits for high operating temperature infrared detectors

A review of high operating temperature (HOT) infrared (IR) photon detector technology vis-a-vis material requirements, device design and state of the art achieved is presented in this article. The HOT photon detector concept offers the promise of operation at temperatures above 120 K to near room temperature. Advantages are reduction in system size, weight, cost and increase in system reliability. A theoretical study of the thermal generation-recombination (g-r) processes such as Auger and defect related Shockley Read Hall (SRH) recombination responsible for increasing dark current in HgCdTe detectors is presented. Results of theoretical analysis are used to evaluate performance of long wavelength (LW) and mid wavelength (MW) IR detectors at high operating temperatures. (C) 2013 Elsevier B.V. All rights reserved.

Thermal test method for high power three-phase grid-connected inverters

Semiconductor device junction temperatures are maintained within datasheet specified limits to avoid failure in power converters. Burn-in tests are used to ensure this. In inverters, thermal time constants can be large and burn-in tests are required to be performed over long durations of time. At higher power levels, besides increased production cost, the testing requires sources and loads that can handle high power. In this study, a novel method to test a high power three-phase grid-connected inverter is proposed. The method eliminates the need for high power sources and loads. Only energy corresponding to the losses is consumed. The test is done by circulating rated current within the three legs of the inverter. All the phase legs being loaded, the method can be used to test the inverter in both cases of a common or independent cooling arrangement for the inverter phase legs. Further, the method can be used with different inverter configurations - three- or four-wire and for different pulse width modulation (PWM) techniques. The method has been experimentally validated on a 24 kVA inverter for a four-wire configuration that uses sine-triangle PWM and a three-wire configuration that uses conventional space vector PWM.

Bicyclo[3.2.0]hepta-1,4,6-triene: synthesis, thermal rearrangement, and anion formation

In order to determine the properties of the bicycloheptatrienyl anion (Ia) (predicted to be conjugatively stabilized by Hückel Molecular Orbital Theory) the neutral precursor, bicyclo[3. 2. 0] hepta-1, 4, 6-triene (I) was prepared by the following route.

Reaction of I with potassium-t-butoxide, potassium, or lithium dicyclohexylamide gave anion Ia in very low yield. Reprotonation of I was found to occur solely at the 1 or 5 position to give triene II, isolated as to its dimers.

A study of the acidity of I and of other conjugated hydrocarbons by means of ion cyclotron resonance spectroscopy resulted in determination of the following order of relative acidities:

H₂S ˃ C₅H₆ ˃ CH₃NO₂ ˃ 1, 4- C₅H₈ ˃ I ˃ C₂H₅OH ˃ H₂O; cyclo-C₇H₈ ˃ C₂ H₅OH; фCH₃ ˃ CH₃OH

In addition, limits for the proton affinities of the conjugate bases were determined:

350 kcal/mole ˂ PA(C₅ H₅^-) ˂ 360 kcal/mole

362 kcal/mole ˂ PA(C₅H₇^-, Ia, cyclo-C₇H₇^-) ˂ 377 kcal/mole PA(фCH₂^-) ˂ 385 kcal/mole

Gas phase kinetics of the trans-XVIII to I transformation gave the following activation parameters: E_a = 43.0 kcal/mole, log A = 15.53 and ∆S^ǂ (220°) = 9.6 cu. The results were interpreted as indicating initial 1,2 bond cleavage to give the 1,3-diradical which closed to I. Similar studies on cis-XVIII gave results consistent with a surface component to the reaction (E_a = 22.7 kcal/mole; log A = 9.23, ∆S^ǂ (119°) = -18.9 eu).

The low pressure (0.01 to 1 torr) pyrolysis of trans-XVIII gave in addition to I, fulvenallene (LV), ethynylcyclopentadiene (LVI) and heptafulvalene (LVII). The relative ratios of the C₇H₆ isomers were found to be dependent upon temperature and pressure, higher relative pressure and lower temperatures favoring formation of I. The results were found to be consistent with the intermediacy of vibrationally excited I and subsequent reaction to give LV and LVI.

Preparation of pH-sensitive polymer by thermal initiation polymerization and its application in fluorescence immunoassay

A fluorescence immunoassay for human IgG (Ag) was developed using a pH-sensitive polymer prepared by thermal initiation or redox initiation polymerization as a carrier. In the competitive immunoassay, appropriate quantity of Ag was immobilized on the polymer and the standard Ag (or sample) solution, and a constant amount of fluorescein isothiocyanate labeled goat anti-human IgG antibody (Ab-FITC) was added. Immobilized Ag and the standard (or sample) Ag competed for binding to the Ab-FITC in 37 C in homogeneous format. After changing the pH to separate the polymer-immune complex precipitate, it was re-dissolved and determined by fluorescence method. The results showed that the immobilization efficiency, immunological reaction activities of immobilized Au and phase transition pH range were improved as Ag was immobilized by thermal initiation instead of redox initiation polymerization. Under optimum conditions, the calibration graphs for the Ag in both methods, thermal initiation and redox initiation, were linear over the concentration range of 0.0-1000 ng mL(-1), with detection limits 8 (thermal initiation) and 12 ng mL(1) (redox initiation), respectively. Moreover, some pH-sensitive polymer prepared only in organic solvent or under high temperature could also be used as an immunoreaction carrier by thermal initiation polymerization. Thermal initiation polymerization was a better immobilization mode. (C) 2004 Elsevier B.V. All rights reserved.

3D Analysis of Heat Transfer Intensification by Re-Entrance Flow Pin-Fins Microstructures with a Highly Thermal-Conductive Plate

Joule heat-induced hot-spot formation sets severe limits in the operation of continuous annular electrochromatography (CAEC), a new concept for preparative separation as an analog to analytical capillary electrochromatography (CEC). This may lead to eluent flow perturbance, even to boiling, which would massively weaken separation efficiency and may even hamper the stationary phase used for separation. For reasons of system integration and high-efficiency heat transfer, micro flow heat exchangers are considered with a separate coolant flow. A 3D numerical analysis of the heat transfer of water single-phase laminar flow in a square microchannel and different arrays of micro pin-fins was carried out using COMSOL Multiphysics. Several advanced materials with low electric conductivity and at the same time with high heat conductivity were put forward to be used in the CAEC system. As essential design point, it is proposed to constitute the micro heat exchanger from two different parts of the CAEC system, namely a microstructured pin-fins plate and a so-called conductive plate.

ENVIRONMENTAL LIMITS ON THE NONRESONANT COSMIC-RAY CURRENT-DRIVEN INSTABILITY

We investigate the so-called nonresonant cosmic-ray streaming instability, first discussed by Bell (2004). The extent to which thermal damping and ion-neutral collisions reduce the growth of this instability is calculated. Limits on the growth of the nonresonant mode in SN1006 and RX J1713.7-3946 are presented.

Application of thermal ion-molecule reactions in tackling spectroscopic inferences in inductively coupled plasma mass spectrometry

Part I: Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N20, and NH3 as reaction gases in ICP-DRC-MS Thermal ion-molecule reactions, targeting removal of specific spectroscopic interference problems, have become a powerful tool for method development in quadrupole based inductively coupled plasma mass spectrometry (ICP-MS) applications. A study was conducted to develop an accurate method for the determination of vanadium in lake sediment samples by ICP-MS, coupled with a dynamic reaction cell (DRC), using two differenvchemical resolution strategies: a) direct removal of interfering C10+ and b) vanadium oxidation to VO+. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for C10+ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH3 did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized Eonditions, creation of VO+ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit (2.7 ng L-1). Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040-1), using two different analytelinterference separation strategies, suggested that the vanadium mono-oxidation offers advantageous performance over the conventional method using NH3 for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications that deal with ultra-trace contaminants.Part II: Validation of a modified oxidation approach for the quantification of total arsenic and selenium in complex environmental matrices Spectroscopic interference problems of arsenic and selenium in ICP-MS practices were investigated in detail. Preliminary literature review suggested that oxygen could serve as an effective candidate reaction gas for analysis of the two elements in dynamic reaction cell coupled ICP-MS. An accurate method was developed for the determination of As and Se in complex environmental samples, based on a series of modifications on an oxidation approach for As and Se previously reported. Rhodium was used as internal standard in this study to help minimize non-spectral interferences such as instrumental drift. Using an oxygen gas flow slightly higher than 0.5 mL min-I, arsenic is converted to 75 AS160+ ion in an efficient manner whereas a potentially interfering ion, 91Zr+, is completely removed. Instead of using the most abundant Se isotope, 80Se, selenium was determined by a second most abundant isotope, 78Se, in the form of 78Se160. Upon careful selection of oxygen gas flow rate and optimization ofRPq value, previous isobaric threats caused by Zr and Mo were reduced to background levels whereas another potential atomic isobar, 96Ru+, became completely harmless to the new selenium analyte. The new method underwent a strict validation procedure where the recovery of a suitable certified reference material was examined and the obtained sample data were compared with those produced by a credible external laboratory who analyzed the same set of samples using a standardized HG-ICP-AES method. The validation results were satisfactory. The resultant limits of detection for arsenic and selenium were 5 ng L-1 and 60 ng L-1, respectively.

Studies on Electrical and Thermal Properties of Certain Selected Photonic Materials

The present thesis is centered around the study of electrical and thermal properties of certain selected photonic materials.We have studied the electrical conduction mechanism in various phases of certain selected photonic materials and those associated with different phase transitions occurring in them. A phase transition leaves its own impressions on the key parameters like electrical conductivity and dielectric constant. However, the activation energy calculation reveals the dominant factor responsible for conduction process.PA measurements of thermal diffusivity in certain other important photonic materials are included in the remaining part of the research work presented in this thesis. PA technique is a promising tool for studying thermal diffusivities of solid samples in any form. Because of its crucial role and common occurrence in heat flow problems, the thermal diffusivity determination is often necessary and knowledge of thermal diffusivity can intum be used to calculate the thermal conductivity. Especially,knowledge of the thermal diffusivity of semiconductors is important due to its relation to the power dissipation problem in microelectronic and optoelectronic devices which limits their performances. More than that, the thermal properties, especially those of thin films are of growing interest in microelectronics and microsystems because of the heat removal problem involved in highly integrated devices. The prescribed chapter of the present theis demonstrates how direct measurement of thermal diffusivity can be carried out in thin films of interest in a simple and elegant manner using PA techniques. Although results of only representative measurements viz; thermal diffusivity values in Indium, Aluminium, Silver and CdS thin films are given here, evaluation of this quantity for any photonic and / electronic material can be carried out using this technique in a very simple and straight forward manner.

What limits insect fecundity? Body size- and temperature-dependent egg maturation and oviposition in a butterfly

1. Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting. 2. Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother’s condition and her egg production might be expected. 3. In the temperate butterfly Pararge aegeria , the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes. 4. The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size. 5. This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects.