bluuebunny/crossref_metadata_2025 huggingface dataset:
The Importance of Effective Root Cause Analysis of Failures in High Reliability Microelectronics Applications: A Case Study
Authors: Schulz Gwen
Published: October 2015

The screening and detection of failures in high reliability electronics is crucial to mission success. The governing standards for microelectronic components prescribe effective screens to address known failure modes during the manufacture of the components. When failures are detected outside of the normal component screening process such as in the next higher assemblies, the analysis of such failures to root cause is even more crucial. Effective root cause analysis requires collaboration among personnel having expertise in many areas, both technical and organizational. Too often, the analysis stops at the ‘how’ a part failed, rather than the ‘why’ and true root cause determination. Failures may not only represent defects in the technical aspects of the design, materials or application of the hardware, but may also be related to human organizational factors such as the competing interests of time, quality and cost. The analysis must extend beyond the forensic data into the human organization and the interaction between people, process and hardware.

In this paper, the author illustrates an effective root cause corrective action (RCCA) analysis process through the discussion of a microelectronics packaging case study. The case involved failure of high reliability hybrid microelectronic components at the next higher assembly level. The case study provides insights into the root cause analysis process as well as awareness that component level high reliability screening is not impervious. It is critical for the next level user to have the expertise in their organization to understand both the how and the why of such failures.

The case study describes a failure related to loose metal particles inside a hermetically sealed multilayer ceramic package which had passed Particle Impact Noise Detection (PIND) screening at the supplier. Root cause analysis determined the cause for the screening escape as well as the cause of the metal particles, and effective corrective actions were implemented at both the component supplier and Honeywell. Technical causes include improper package design, weld schedule and screening methods. Organizational causes include inadequate documentation, lack of training and failure to react to prior failures. The root cause investigation team was a multi-discipline group from Honeywell, our customer, and the component supplier, with additional consulting input from other suppliers, equipment manufacturers and industry experts.
160 MILLI-OHM ELECTRICAL RESISTANCE THRU-WAFER INTERCONNECTS WITH 10:1 ASPECT RATIO
Authors: Efimovskaya A. , Shkel A.M.
Published: October 2015

We present a novel approach for high-aspect ratio low resistance Thru-Wafer Interconnects for Double-Sided (TWIDS) fabrication of MicroElectroMechanical Systems (MEMS). The interconnects are formed by etching blind via holes in the handle substrate of an SOI (Silicon on Insulator) wafer, followed by filling the holes with copper, using sonic-assisted seedless copper electroplating process. This technique does not require additional conductive layer deposition, but utilizes a highly doped silicon device layer as a seed. The donut-shape gaps are etched around the copper filled vias to provide interconnects insulation. We introduced the fabrication process and characterized the performance of interconnects. Experimental analysis of an array of 22 interconnects demonstrated that the resistance values as low as 160 milli-Ohm can be achieved. Parasitic capacitance of interconnects is analytically calculated and the distortion of the MEMS resonator transduction spectrum is predicted using an equivalent circuit model. Signal amplitude and phase distortion due to the parasitic capacitance are estimated to be 1.15 dB and 5.96 deg, respectively, for the optimum 60 um diameter via with 35 um insulating gap. The method presented is compatible with an in-house folded MEMS fabrication process and may enable 3D folded TIMU (Timing Inertial Measurement Unit) structures with thru-wafer interconnects.
A Non-destructive Bulk Currency Detection System (BCDS) for Screening Smuggled Currency
Authors: Stetter J. R. , Carter M.T. , Findlay M.W. , Li Suiqiong , Papageorge Marc
Published: October 2015

Bulk cash smuggling is a serious issue in recent years. It is estimated that $6–36B flow illegally between the United States and Mexico each year during otherwise legitimate border crossings. A nondestructive bulk currency detection system (BCDS) for screening pedestrians, vehicles and shipping containers will significantly improve boarder security, protect domestic economics and deter criminal and terrorist activity. However, such a practical device is not yet available because neither the target detection technique nor the instrumentation has been defined. In this paper, we evaluated the currency characteristics that provide a basis for detection, relevant physical/chemical instrumental approaches, and a rationale for selection of an approach to build a practical BCDS. US currency releases volatile compounds. These emissions can be used as a chemical signature in currency detection. The literature regarding characterization of volatile compounds associated with US currency is limited. To identify the unique vapor signature of US currency, we analyzed VOC emission from currency bills using thermal desorption GC/MS. This enabled calculation of emission rates of volatile compounds. The results were consistent with prior studies of currency emissions. From our data and the literature, a tentative fingerprint that represents currency can be selected from among the complex background present in real currency. The analysis shows that a most-likely US currency vapor signature contains a specific set of volatiles at low concentrations. A successful practical BCDS based on volatiles must be able to accurately identify and quantify a speciated set of trace chemicals from a complex and highly variable matrix. Variations of GC/MS with SPME preconcentration can result in near-term methods. Future developments are needed to address optimization of methodology and meet the need for rapid sampling, detection with speciation. Sensor arrays can also provide a platform for currency detection and would improve logistics over larger instruments.
Design of a Miniaturized Vibrating Beam Power Converter
Authors: Marinis Thomas F. , Soucy Joseph W.
Published: October 2015

One of the largest components on miniaturized, multichip modules is the chip inductor associated with the onboard DC to DC power converter. It is an essential component for efficient conversion of the system voltage to the operating voltage of the module. In a previous paper, we described how vibrating capacitor structures could be used to perform inductor functions. In this paper, we focus on the specific application of an on-board power converter. Our vision is for a MEMS scale device that could be attached to the back of a chip as an appliqué or embedded in an interposer on which the chip was mounted. It would function as a DC to DC converter to extract power from the system buss and supply it to the chip at its required operating voltage.

This device consists of a long, flat, rectangular, vibrating beam that is sandwiched between two fixed electrodes. It is clamped at its two ends and electrically connected to ground. On one of the fixed electrodes, which we refer to as the source electrode, a bias potential is applied through a resistor connected to a battery. The motion of the beam relative to the source electrode generates a sinusoidal like fluctuation in the potential between them. The amplitude of this alternating voltage is set by the amplitude of the beam vibration and the nominal gap between the beam and source electrode. It can be made insensitive to variations in battery voltage, by controlling the amplitude of the beam vibrations. The sinusoidal portion of the bias voltage can be extracted through a DC blocking capacitor connected to the source electrode. By passing it through a rectifier and filter capacitor, it can be used as a stable DC supply voltage.

The beam vibration is initiated and sustained by voltage pulses applied to the other fixed electrode, which we refer to as the drive electrode. A logic circuit connected to the source electrode monitors its sinusoidal voltage and applies a pulse to the drive electrode when two criteria are met. First, the sinusoidal voltage must be rising, which occurs when the beam is moving away from the source electrode and towards the drive electrode. Second, the time average of the sinusoidal voltage must be below its desired set point, which means that more energy must be injected into the beam. When voltage is applied to the drive electrode, it exerts a force on the vibrating beam that pulls it towards the drive electrode.

We have constructed a Mat Lab model of a vibrating beam power converter and have been using it to examine a number of design factors including, physical size, vibration frequency and amplitude, values for the DC blocking and output filter capacitors, as well as the logic used to apply pulses to the drive electrode. Our intent is to develop a sufficient understanding of the device operational and physical design requirements to enable us to build a prototype device.
Composition and Form: How Feedthrough Design Affects Package Hermeticity
Authors: Share Richard R.
Published: October 2015

Ceramic-insulated feedthroughs have been in use in microelectronic packages for decades. Their track record is generally good, but not unblemished. This is because ceramic insulators tend to crack under stress - the stress of assembly temperatures, thermal shock screening and fine leak pressurization. The cracks often propagate to surface termination, forming leak paths and rendering afflicted packages non-hermetic. Package manufacturers have long battled this phenomenon and developed a number of creative designs that attempt to prevent, minimize and/or contain this inherent vulnerability. Yet it persists.

To successfully prevent this undesired effect, the factors causal to its origination must be identified, understood and eliminated. That is to say, the effects of the constituent components or parts – the package wall, insulator, conductor and brazes – in summation and subtraction, in function and failure, on the integrity and reliability of the whole must be understood in order to design a package robust to thermal and pressural excursions. The optimal design will consist of components with complimentary properties of composition and form; properties that in interaction with one another multiplicatively enhance package robustness and reliability. Any other design will be vulnerable to failure.

Herein, the effects of the component properties of composition and form on the structural integrity, reliability and hermeticity of metal cases employing ceramic insulators will be discussed, the primary factors causal to contemporary feedthrough hermeticity failures will be introduced in the form of a simplified force model, an optimization case study will be presented in brief, and currently utilized design features will be objectively compared and assessed.
Nanofabricated Electronic Components
Authors: Edwards Carl , Jin Sungho , Gardner Calvin
Published: October 2015

For many military applications, domestic sourcing for passive electronic components are required. Organizations wrestling with the loss of domestic electronic parts producers, have a solution in nano fabricated components. This highly reliable technology employs the use of COTS raw materials sets, mitigating development risk. Application flexible, existing surface mounted components can be replaced with this superior technology. The unique construction of this nano fabricated product enables board space reductions exceeding 65%, a critical advantage in space applications.
Assembly and Scaling Challenges for 2.5D IC
Authors: Wang Liang , Woychik Charles G. , Gao Guilian , McGrath Scott , Shen Hong , Tosaya Eric , Arkalgud Sitaram
Published: October 2015

2.5D technology is gaining acceptance in the industry and an increasing number of products are beginning to enter volume manufacturing. As with all interconnect technologies, the key metrics driving the transition include higher computing performance, lower power consumption, smaller form factor, increased bandwidth and reduced latency (interconnect delay). In order to transition from today's low volumes to High Volume Manufacturing (HVM), the concerns of warpage control, thermal dissipation, cost (yield and throughput) and overall technology scalability for future generations need to be addressed rapidly. The solutions in these relatively new packaging technologies encompass design/layout, material, process and integration choices.

With these concerns as a backdrop, our paper will discuss our approach to optimizing 2.5D assembly for HVM. We will begin with a review of our test vehicle and our overall choices of substrate, interposer and die dimensions. Three different 2.5D assembly approaches that have been investigated at Invensas for warpage control, ease of process, and impact on yield and reliability will be discussed in detail. We will present our results from critical areas including temporary bonding, thermo-compression bonding, mass reflow, thin wafer/die handling, flux, underfill and molding. This paper will present our understanding of the underlying principles governing the technology bottlenecks in advanced packaging and the three flows will be compared with an assessment of their advantages and disadvantages. In addition, we will also provide the results of our cost modeling work. We will finish by making recommendations for an optimized assembly process flow.
Improved Fabrication of Micro Channels in LTCC Circuitry and MEMS Using QPAC® Polyalkylene Carbonate as a Sacrificial Structure
Authors: Ferraro Peter
Published: October 2015

QPAC® Polyalkylene carbonates polymers are currently used as a sacrificial material in many applications because they decompose at very low temperatures and leave virtually no contamination or residual behind after the debind step. This includes applications for air gaps in microfluidics, micro electro mechanical systems and microelectronics. QPAC® decomposition properties are very critical in applications with temperature sensitive materials or where residuals can cause electrical and or mechanical problems in the final product. Past work by academia and industry has been done with QPAC® to make enclosed air channels by providing temporary scaffolding in the pattern of the air gap. There are several methods of forming a cavity in an electronic device. This includes removal of the sacrificial material by thermal decomposition and wet etching. Thermal decomposition is the method employed to form the cavity using QPAC®. The results have been promising and show that this is a viable method to fabricate air gaps in Microelectromechanical, MEM systems and LTCC modules. Several new Polyalkylene carbonate polymers have recently been commercially produced to support further growth into this area.
Laser Ablation of Thin Films on LTCC
Authors: Girardi M. A. , Peterson K. A. , Vianco P. T. , Grondin R. , Wieliczka D.
Published: October 2015

Direct Digital Manufacturing techniques such as laser ablation are proposed for the fabrication of lower cost, miniaturized, and lightweight integrated assemblies with high performance requirements. This paper investigates the laser ablation of a Ti/Cu/Pt/Au thin film metal stack on fired low temperature cofired ceramic (LTCC) surfaces using a 355 nm Nd:YAG diode pumped laser ablation system. It further investigates laser ablation applications using unfired, or ‘green’, LTCC materials: (1) through one layer of a laminated stack of unfired LTCC tape to a buried thick film conductor ground plane, and (2) in unfired Au thick films. The UV laser power profile and part fixturing were optimized to address defects such as LTCC microcracking, thin film adhesion failures, and redeposition of Cu and Pt. An alternate design approach to minimize ablation time was tested for efficiency in manufacture. Multichip Modules (MCM) were tested for solderability, solder leach resistance, and wire bondability. Scanning electron microscopy (SEM) as well as cross sections and microanalytical techniques were used in this study.
IMS (Injection Molded Solder) Technology with Liquid Photoresist for Ultra Fine Pitch Bumping
Authors: Aoki Toyohiro , Toriyama Kazushige , Mori Hiroyuki , Orii Yasumitsu , Nah Jae-Woong , Takahashi Seiichirou , Mukawa Jun , Hasegawa Kouichi , Kusumoto Shiro , Inomata Katsumi
Published: October 2015

IMS (injection molded solder) is an advanced solder bumping technology with solder alloy flexibility even at very fine pitch and small size. One of key materials for successful fine pitch bumping by IMS is a photoresist material. The photoresist material must be stable at high temperature during the IMS process and be perfectly stripped after the IMS process without any residue on the surface of the substrate. In this study, negative tone liquid photoresist materials were prepared to investigate effects of thermal cure of photoresist on IMS process and stripping performance. With appropriate cure conditions, successful bumping without any film damages at IMS process and any residue at stripping was achieved. Fine pitch bumping down to 40 μm pitch with 20 μm diameter was demonstrated with a Sn-3.0Ag-0.5Cu solder. Also physical and electrical connections for the solder joints of IMS bumps to Ni/Au pads were confirmed using a 80 μm pitch test vehicle.
Cost Comparison of Temporary Bond and Debond Methods For Thin Wafer Handling
Authors: Palesko Amy
Published: October 2015

Miniaturization and increased performance demands are driving the industry to explore 2.5D and 3D packaging. Although progress has been made in recent years, many barriers remain. One primary cost driver for 2.5D and 3D processes is the temporary bond and debond method used for thin wafer handling. Various solutions are appearing on the market, but there is not a single method taking the lead as the obvious best choice. Many factors must be considered when looking at the total cost of a thin wafer handling solution. In this paper, we will use cost modeling to carry out detailed cost and yield trade-offs for temporary bond and debond methods. Instead of concentrating on one proposed solution that is available on the market, we will analyze a range of solutions, focusing on variables such as tool cost, material cost, throughput, yield, and interposer cost. With this analysis, we will determine the most significant cost drivers within the temporary bond and debond process and propose process details for a reasonable solution.
Extreme Power Considerations for High Performance Computing
Authors: Lin How
Published: October 2015

Power demand in the high end computing and data server segments are driving higher power delivery requirements at all packaging levels in a typical system. At the compute device level, compute node cards are now requiring core power supplies with current levels well above 100 amps at 1 volt or less. This imposes severe power delivery challenges in both power supply power conversion efficiency improvement and power delivery path loss minimization. Due to substantial aggregate I2R losses introduced by the current carrying structures in the power delivery paths, depending on the current level used, up to 10% and more of power loss could result. The focus of this paper is in the discussion of novel interconnect structures developed for reduction of current delivery path power loss. i3Electronics Research & Development addresses these extremes with packaging constructs capable of efficient handling in excess of 200 amps at the device level. Through the course of this study, methods were developed for thermal and electrical modeling, dynamic test apparatus and testing. Several test vehicles were built based on concepts with promising modeled results. Power loss / efficiency, thermal dynamics and electrical dynamics were measured using these test vehicles. The measured and modeled results were compared and studied to assess the accuracy of the power delivery network modeling methodology. This paper will present the methods and constructs developed along with the models and test results.
CHRONIC LYMPHOCYTIC LEUKAEMIA: CENSUS OF PATIENTS TREATED IN ITALIAN HAEMATOLOGY UNITS
Authors: Salvi Gianfranco
Published: October 2015

This study was conducted by contacting the population of the Italian haematology units and collecting from 68% of them data concerning the number of patients with chronic lymphocytic leukaemia visited over the previous 12 months, with the aim of obtaining an overview of the treatment of this disease and comparing the results with the prevalence estimates found in literature.The projection obtained (about 17,000 patients visited in the previous 12 months) is probably overestimated because of double-counting of patients who may have been treated at two different facilities during the year, although it is also underestimated since the internal medicine units were not involved. The balance of these two opposite factors is not known.It is important to bear in mind the approximation with which the count was performed in facilities for which no official data were available.Albeit with these limits, the results obtained are in line with some existing prevalence data and make it possible to determine the portion of patients at different Binet stages and in the various age ranges, identifying the corresponding therapeutic treatments. Use of the CIRS scale to classify patients as FIT and UNFIT was seen to be still somewhat limited.
Predicting the mineral composition of dust aerosols – Part 1: Representing key processes
Authors: Perlwitz J. P. , Pérez García-Pando C. , Miller R. L.
Published: October 2015

Abstract. Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.
Wet deposition of atmospheric inorganic nitrogen at five remote sites in the Tibetan Plateau
Authors: Liu Y. W. ,   Xu-Ri, Wang Y. S. , Pan Y. P. , Piao S. L.
Published: October 2015

Abstract. Since the mid-20th century, nitrogen (N) deposition has shown an increasing trend in the Tibetan Plateau (TP), where alpine ecosystems are sensitive to elevated N deposition. However, the quantitative characterization of N deposition in the TP remains unclear, due in most part to the lack of in situ measurement. Using the Tibetan Observation and Research Platform network, we conducted short-term in situ measurements of major ions (NO3−, Cl−, SO42−, NH4+, Na+, K+, Ca2+, and Mg2+) wet deposition at five remote sites in the TP during 2011–2013. At Southeast Tibet Station, Nam Co Station, Qomolangma Station, Ngari Station, and Muztagh Ata Station, the NH4+–N wet deposition was 0.63, 0.68, 0.92, 0.36, and 1.25 kg N ha−1 yr−1, respectively; the NO3−–N wet deposition was 0.28, 0.24, 0.03, 0.08, and 0.30 kg N ha−1 yr−1, respectively; and the inorganic N wet deposition was 0.91, 0.92, 0.94, 0.44, and 1.55 kg N ha−1 yr−1, respectively. The inorganic N wet deposition mainly occurred in the form of NH4+–N during summer at all sites. Results of enrichment factor analysis and principal component analysis demonstrated that both NH4+–N and NO3−–N wet deposition in the TP were mainly influenced by anthropogenic activities. Backward trajectory analysis showed that the inorganic N deposition at Muztagh Ata Station was mainly transported from central Asia and the Middle East through westerlies. At Southeast Tibet Station, Nam Co Station, Qomolangma Station, and Ngari Station, the inorganic N deposition was mainly contributed by anthropogenic sources in south Asia, and was mainly transported by the Indian monsoon. Combining site-scale in situ measurements of inorganic N wet deposition in this and previous studies, the average wet deposition of atmospheric NH4+–N, NO3−–N, and inorganic N in the TP was estimated to be 1.06, 0.51, and 1.58 kg N ha−1 yr−1, respectively. The average NH4+–N : NO3−–N ratio in precipitation in the TP was approximately 2 : 1. Results from the present study suggest that earlier estimations based on chemical transport model simulations and/or limited field measurements likely overestimated substantially the regional inorganic N wet deposition in the TP. To clarify the total N deposition in the TP more clearly, it is essential to conduct long-term monitoring of both wet and dry deposition of atmospheric N in various climate zones in the TP in the future.
Interdependencies between temperature and moisture sensitivities of CO2 emissions in European land ecosystems
Authors: Gritsch C. , Zimmermann M. , Zechmeister-Boltenstern S.
Published: October 2015

Abstract. Soil respiration is one of the largest terrestrial fluxes of carbon dioxide (CO2) to the atmosphere. Hence, small changes in soil respiration rates could have large effects on atmospheric CO2. In order to assess CO2 emissions from diverse European soils with different land-use types and climate (soil moisture and temperature), we conducted a laboratory incubation experiment. Emission measurements of CO2 under controlled conditions were conducted using soil monoliths of nine sites from a European flux network (ÉCLAIRE). The sites are located all over Europe – from the United Kingdom in the west to Ukraine in the east, and from Italy in the south to Finland in the north – and can be separated according to four land-use types (forests, grasslands, arable lands and one peatland). Intact soil cores were incubated in the laboratory in a two-way factorial design, with temperature (5, 10, 15, 20 and 25 °C) and water-filled pore space (WFPS; 5, 20, 40, 60 and 80 %) as the independent variables, while CO2 flux was the response variable. The latter was measured with an automated laboratory incubation measurement system. Land use generally had a substantial influence on carbon dioxide fluxes, with the order of CO2 emission rates of the different land-use types being grassland > peatland > forest/arable land (P < 0.001). CO2 efflux responded strongly to varying temperature and moisture content with optimum moisture contents for CO2 emissions between 40 and 70 % WFPS and a positive relationship between CO2 emissions and temperature. The relationship between temperature and CO2 emissions could be well described by a Gaussian model. Q10 values ranged between 0.86 and 10.85 and were negatively related to temperature for most of the moisture contents and sites investigated. At higher temperatures the effect of water and temperature on Q10 was very low. In addition, under cold temperatures Q10 varied with moisture contents, indicating a stronger prospective effect of rain events in cold areas on temperature sensitivity. At both coniferous forest sites we found a strong increase in the temperature sensitivity at a moisture range between 20 and 40 % WFPS. We developed a new approach to calculate moisture sensitivity (MS) of CO2 efflux. MS was calculated as the slope of a polynomial function of second degree. Moisture sensitivities were highest under dry and wet conditions. In addition we found a positive relationship between MS of CO2 efflux and temperature for both arable lands.
Groundwater-dependent ecosystems: recent insights from satellite and field-based studies
Authors: Eamus D. , Zolfaghar S. , Villalobos-Vega R. , Cleverly J. , Huete A.
Published: October 2015

Abstract. Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs. We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream. We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources. Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.
Modelling evapotranspiration during precipitation deficits: identifying critical processes in a land surface model
Authors: Ukkola A. M. , Pitman A. J. , Decker M. , De Kauwe M. G. , Abramowitz G. , Kala J. , Wang Y.-P.
Published: October 2015

Abstract. Surface fluxes from land surface models (LSM) have traditionally been evaluated against monthly, seasonal or annual mean states. The limited ability of LSMs to reproduce observed evaporative fluxes under water-stressed conditions has been previously noted, but very few studies have systematically evaluated these models during rainfall deficits. We evaluated latent heat flux simulated by the Community Atmosphere Biosphere Land Exchange (CABLE) LSM across 20 flux tower sites at sub-annual to inter-annual time scales, in particular focusing on model performance during seasonal-scale rainfall deficits. The importance of key model processes in capturing the latent heat flux are explored by employing alternative representations of hydrology, leaf area index, soil properties and stomatal conductance. We found that the representation of hydrological processes was critical for capturing observed declines in latent heat during rainfall deficits. By contrast, the effects of soil properties, LAI and stomatal conductance are shown to be highly site-specific. Whilst the standard model performs reasonably well at annual scales as measured by common metrics, it grossly underestimates latent heat during rainfall deficits. A new version of CABLE, with a more physically consistent representation of hydrology, captures the variation in the latent heat flux during seasonal-scale rainfall deficits better than earlier versions but remaining biases point to future research needs. Our results highlight the importance of evaluating LSMs under water-stressed conditions and across multiple plant functional types and climate regimes.
Earthquake source parameters that display the first digit phenomenon
Authors: Toledo P. A. , Riquelme S. R. , Campos J. A.
Published: October 2015

Abstract. We study the main parameters of earthquakes from the perspective of the first digit phenomenon: the nonuniform probability of the lower first digit different from 0 compared to the higher ones. We found that source parameters like coseismic slip distributions at the fault and coseismic inland displacements show first digit anomaly. We also found the tsunami runups measured after the earthquake to display the phenomenon. Other parameters found to obey first digit anomaly are related to the aftershocks: we show that seismic moment liberation and seismic waiting times also display an anomaly. We explain this finding by invoking a self-organized criticality framework. We demonstrate that critically organized automata show the first digit signature and we interpret this as a possible explanation of the behavior of the studied parameters of the Tohoku earthquake.
Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar
Authors: Drews R. , Brown J. , Matsuoka K. , Witrant E. , Philippe M. , Hubbard B. , Pattyn F.
Published: October 2015

Abstract. The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g. temperature and surface mass balance) causing spatial and temporal variations in density–depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth–density relationship, we show that the depth to internal reflectors, the local ice thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the ice-shelf channel should be accounted for when using the hydrostatic ice thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.
Identification guide to Nordic aphids associated with mosses, horsetails and ferns (Bryophyta, Equisetophyta, Polypodiophyta) (Insecta, Hemiptera, Aphidoidea)
Authors: Albrecht Anders Christian
Published: October 2015

Keys and diagnoses of North European aphids (Hemiptera, Aphidoidea) associated with mosses, horsetails and ferns are given, based on fresh and freeze-dried material. Numerous externally visible and thus informative characters, that are absent in cleared, slide-mounted specimens, such as body shape colours, wax coating and pattern etc., are utilized. Most of the species are illustrated by photographs of live specimens and drawings. Root-feeding species living in the moss layer or otherwise often present in moss samples are also included, even if their hosts were spermatophytes. The combination of colour images and diagnoses, utilizing easily observed characters, allows the identification of a large number of species already in the field, and many more at home with the aid of a stereo microscope. Host plant relationships and association with ants are summarised, including new records. Brief accounts on aphid life cycles, freeze-drying preparation techniques, etc. are also given to support the use of the keys.
Effects of Bio-Pesticides on Biology of Chrysoperla carnea F. (Neuroptera: Chrysopidae)
Authors: S. Shahzad Ali  ,  M.Y. Khaskheli  , S. Sohail Ahmed  , Huma Rizwana  , Aslam Bukero  ,  Gulzar Thebo  , Shahzad Ali Nahyo  , Irshad Ali Rattar  , Sarfraz Ahmad
Published: October 2015

The experiment was conducted on effects of bio-pesticides on biology of Chrysoperla carnea F. under laboratory conditions. The neem and datura leaf extracts were used as bio-pesticides and their effect was compared with confidor at 26±2°C, 65±5% R. H and photoperiod (16L: 8D) in the | department of Entomology, Sindh Agriculture University, Tandojam, Pakistan during 2014. The results shows that the incubation periods of eggs of C. carnea feeding on Aphis gossypii treated with neem, datura and confidor was 2.2, 2.5 and 3.6 days respectively. The result indicated that the total larval developmental period was 17.03, 13.3 and 15.09, respectively. The pupal period of C. carnea was 8.82 on neem, 10.9 on datura and 12.33 days on confidor. The result further revealed that the pre oviposition period of C. carnea was 6.35 on neem, 5.5 on datura and 3.6 on confidor. The oviposition period was 34.42 on neem, 30.6 on datura and 26.4 on confidor. The post oviposition period was significantly different was 8.5 days on neem 6.9 on datura and 4.7 on confidor. The maximum fecundity per female of C. carnea was 448.38 days on neem, 435.67 on datura and 413.67 on confidor. Similarly, maximum egg hatching percentage of C.carnea was recorded on neem followed by datura and confidor. However, the maximum egg mortality (37.65%) was recorded on confidor. However, minimum mortality of 1st, 2nd and 3rd instar larvae was recorded due to neem leaf extracts followed by datura and confidor. The pupal mortality was seen more on neem followed by datura and confidor. The highest adult mortality was obtained on neem followed by datura and confidor insecticide.
Owning your mistakes
Authors: Marder Eve
Published: October 2015

Most scientists admit to their errors but, as Eve Marder explains, the scientific community as a whole needs to rethink the way it recognizes achievement.
Noble gas signatures in Greenland: Tracing glacial meltwater sources
Authors: Niu Yi , Castro M. Clara , Aciego Sarah M. , Hall Chris M. , Stevenson Emily I. , Arendt Carli A. , Das Sarah B.
Published: October 2015

This study represents the first comprehensive noble gas study in glacial meltwater from the Greenland Ice Sheet. It shows that most samples are in disequilibrium with surface collection conditions. A preliminary Ne and Xe analysis suggests that about half of the samples equilibrated at a temperature of ~0°C and altitudes between 1000 m and 2000 m, with a few samples pointing to lower equilibration altitudes and temperatures between 2°C and 5°C. Two samples suggest an origin as melted ice and complete lack of equilibration with surface conditions. A helium component analysis suggests that this glacial meltwater was isolated from the atmosphere prior to the 1950s, with most samples yielding residence times ≤ 420 years. Most samples represent a mixture between a dominant atmospheric component originating as precipitation and basal meltwater or groundwater, which has accumulated crustal 4He over time.
Velocity‐ and slip‐dependent weakening in simulated fault gouge: Implications for multimode fault slip
Authors: Ito Yoshihiro , Ikari Matt J.
Published: October 2015

In addition to the velocity dependence of friction, slip dependence may play a major role before and during earthquake slip in fault zones. We performed laboratory friction experiments on simulated fault gouges, measuring both the velocity and slip dependence of friction in velocity step tests. The pure velocity‐dependent component of friction measured over short displacements shows both velocity strengthening and velocity weakening friction, depending on the amount of slip considered. However, we observe that increases in sliding velocity can induce slip weakening behavior which overwhelms the velocity dependence resulting in large overall weakening, especially at rates > 1 µm/s. On natural tectonic faults, this suggests that a velocity perturbation, such as coseismic rupture propagating onto a fault patch, could induce instability via large slip weakening. Therefore, a fault which is experiencing a transient slip or slow earthquakes may be more easily induced to slip coseismically if a dynamic rupture from large earthquake propagates onto the fault.
Positive trends in Southern Hemisphere carbonyl sulfide
Authors: Kremser Stefanie , Jones Nicholas B. , Palm Mathias , Lejeune Bernard , Wang Yuting , Smale Dan , Deutscher Nicholas M.
Published: October 2015

Transport of carbonyl sulfide (OCS) from the troposphere to the stratosphere contributes sulfur to the stratospheric aerosol layer, which reflects incoming short‐wave solar radiation, cooling the climate system. Previous analyses of OCS observations have shown no significant trend, suggesting that OCS is unlikely to be a major contributor to the reported increases in stratospheric aerosol loading and indicating a balanced OCS budget. Here we present analyses of ground‐based Fourier transform spectrometer measurements of OCS at three Southern Hemisphere sites spanning 34.45°S to 77.80°S. At all three sites statistically significant positive trends are seen from 2001 to 2014 with an observed overall trend in total column OCS at Wollongong of 0.73 ± 0.03%/yr, at Lauder of 0.43 ± 0.02%/yr, and at Arrival Heights of 0.45 ± 0.05%/yr. These observed trends in OCS imply that the OCS budget is not balanced and could contribute to constraints on current estimates of sources and sinks.
Distinct effects of global mean warming and regional sea surface warming pattern on projected uncertainty in the South Asian summer monsoon
Authors: Chen Xiaolong , Zhou Tianjun
Published: October 2015

Significant uncertainties in the projected South Asian summer monsoon (SASM) have been observed in the released Fifth Phase of the Coupled Model Intercomparison Project (CMIP5) data set. Knowing what factors dominate the uncertainties is critical to constraining the local climate changes. Analyzing state‐of‐the‐art climate model simulations under the RCP8.5 scenario, we find that uncertainties in the circulation primarily result from the divergent global mean warming across models. In contrast, the compensation between dynamic and thermodynamic effects makes the spread in monsoon rainfall independent of the global temperature change. Via a suite of sensitivity experiments, we identify that the uncertainties in the SASM rainfall are dominated by the Indo‐Pacific sea surface temperature (SST) warming pattern, especially around the western central Pacific. The SST warming pattern plays its role by changing the zonal temperature gradient over the SASM region and modulating the interhemispheric moisture transport. We highlight that the SST warming patterns require more attention in constraining the projected regional rainfall changes.
High‐resolution in situ observations of electron precipitation‐causing EMIC waves
Authors: Rodger Craig J. , Hendry Aaron T. , Clilverd Mark A. , Kletzing Craig A. , Brundell James B. , Reeves Geoffrey D.
Published: October 2015

Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering‐driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite‐based observations of the characteristics of EMIC waves, with satellite and ground‐based observations of the EMIC‐induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC‐induced electron precipitation inferred from coincident precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. These observations will better constrain modeling into the importance of EMIC wave‐particle interactions.
Responses of relativistic electron fluxes in the outer radiation belt to geomagnetic storms
Authors: Xiong Ying , Xie Lun , Pu Zuyin , Fu Suiyan , Chen Lunjin , Ni Binbin , Li Wen , Li Jinxing , Guo Ruilong , Parks G. K.
Published: October 2015

Geomagnetic storms can either increase or decrease relativistic electron fluxes in the outer radiation belt. A statistical survey of 84 isolated storms demonstrates that geomagnetic storms preferentially decrease relativistic electron fluxes at higher energies, while flux enhancements are more common at lower energies. In about 87% of the storms, 0.3–2.5 MeV electron fluxes show an increase, whereas 2.5–14 MeV electron fluxes increase in only 35% of the storms. Superposed epoch analyses suggest that such “energy‐dependent” responses of electrons preferably occur during conditions of high solar wind density which is favorable to generate magnetospheric electromagnetic ion cyclotron (EMIC) waves, and these events are associated with relatively weaker chorus activities. We have examined one of the cases where observed EMIC waves can resonate effectively with >2.5 MeV electrons and scatter them into the atmosphere. The correlation study further illustrates that electron flux dropouts during storm main phases do not correlate well with the flux buildup during storm recovery phases. We suggest that a combination of efficient EMIC‐induced scattering and weaker chorus‐driven acceleration provides a viable candidate for the energy‐dependent responses of outer radiation belt relativistic electrons to geomagnetic storms. These results are of great interest to both understanding of the radiation belt dynamics and applications in space weather.