José M. de la Rosa

Comparison of quantification methods to measure fire‐derived (black/elemental) carbon in soils and sediments using reference materials from soil, water, sediment and the atmosphere

Black carbon (BC), the product of incomplete combustion of fossil fuels and biomass (called elemental carbon (EC) in atmospheric sciences), was quantified in 12 different materials by 17 laboratories from different disciplines, using seven different methods. The materials were divided into three classes: (1) potentially interfering materials, (2) laboratory-produced BC-rich materials, and (3) BC-containing environmental matrices (from soil, water, sediment, and atmosphere). This is the first comprehensive intercomparison of this type (multimethod, multilab, and multisample), focusing mainly on methods used for soil and sediment BC studies. Results for the potentially interfering materials (which by definition contained no fire-derived organic carbon) highlighted situations where individual methods may overestimate BC concentrations. Results for the BC-rich materials (one soot and two chars) showed that some of the methods identified most of the carbon in all three materials as BC, whereas other methods identified only soot carbon as BC. The different methods also gave widely different BC contents for the environmental matrices. However, these variations could be understood in the light of the findings for the other two groups of materials, i.e., that some methods incorrectly identify non-BC carbon as BC, and that the detection efficiency of each technique varies across the BC continuum. We found that atmospheric BC quantification methods are not ideal for soil and sediment studies as in their methodology these incorporate the definition of BC as light-absorbing material irrespective of its origin, leading to biases when applied to terrestrial and sedimentary materials. This study shows that any attempt to merge data generated via different methods must consider the different, operationally defined analytical windows of the BC continuum detected by each technique, as well as the limitations and potential biases of each technique. A major goal of this ring trial was to provide a basis on which to choose between the different BC quantification methods in soil and sediment studies. In this paper we summarize the advantages and disadvantages of each method. In future studies, we strongly recommend the evaluation of all methods analyzing for BC in soils and sediments against the set of BC reference materials analyzed here.

Sigma-Delta Modulators: Tutorial Overview, Design Guide, and State-of-the-Art Survey

This paper presents a tutorial overview of ΣΔ modulators, their operating principles and architectures, circuit errors and models, design methods, and practical issues. A review of the state of the art on nanometer CMOS implementations is described, giving a survey of cutting-edge ΣΔ architectures, with emphasis on their application to the next generation of wireless telecom systems.

CMOS sigma-delta converters : practical design guide

This book presents a systematic and comprehensive compilation of sigma-delta converter operating principles, the new advances in architectures and circuits, design methodologies and practical considerations # going from system-level specifications to silicon integration, packaging and measurements, with emphasis on nanometer CMOS implementation. The book emphasizes practical design issues – from high-level behavioural modelling in MATLAB/SIMULINK, to circuit-level implementation in Cadence Design FrameWork II. As well as being a comprehensive reference to the theory, the book is also unique in that it gives special importance on practical issues, giving a detailed description of the different steps that constitute the whole design flow of sigma-delta ADCs.

Relating physical and chemical properties of four different biochars and their application rate to biomass production of Lolium perenne on a Calcic Cambisol during a pot experiment of 79 days.

Three pyrolysis biochars (B1: wood, B2: paper-sludge, B3: sewage-sludge) and one kiln-biochar (B4: grapevine wood) were characterized by determining different chemical and physical properties which were related to the germination rates and to the plant biomass production during a pot experiment of 79 days in which a Calcic Cambisol from SW Spain was amended with 10, 20 and 40 t ha(-1) of the four biochars. Biochar 1, B2 and B4 revealed comparable elemental composition, pH, water holding capacity and ash content. The H/C and O/C atomic ratios suggested high aromaticity of all biochars, which was confirmed by (13)C solid-state NMR spectroscopy. The FT-IR spectra confirmed the aromaticity of all the biochars as well as several specific differences in their composition. The FESEM-EDS distinguished compositional and structural differences of the studied biochars such as macropores on the surface of B1, collapsed structures in B2, high amount of mineral deposits (rich in Al, Si, Ca and Fe) and organic phases in B3 and vessel structures for B4. Biochar amendment improved germination rates and soil fertility (excepting for B4), and had no negative pH impact on the already alkaline soil. Application of B3, the richest in minerals and nitrogen, resulted in the highest soil fertility. In this case, increase of the dose went along with an enhancement of plant production. Considering costs due to production and transport of biochar, for all used chars with the exception of B3, the application of 10 t ha(-1) turned out as the most efficient for the crop and soil used in the present incubation experiment.

Adaptive CMOS analog circuits for 4G mobile terminals-Review and state-of-the-art survey

The fourth-generation (4G) of cellular terminals will integrate the services provided by previous generations second-generation/third-generation (2G/3G) with other applications like global positioning system (GPS), digital video broadcasting (DVB) and wireless networks, covering metropolitan (IEEE 802.16), local (IEEE 802.11) and personal (IEEE 802.15) areas. This new generation of hand-held wireless devices, also named always-best-connected systems, will require low-power and low-cost multi-standard chips, capable of operating over different co-existing communication protocols, signal conditions, battery status, etc. Moreover, the efficient implementation of these chipsets will demand for reconfigurable radio frequency (RF) and mixed-signal circuits that can adapt to the large number of specifications with minimum power dissipation at the lowest cost. Nanometer CMOS processes are expected to be the base technologies to develop 4G systems, assuring mass production at low cost through increased integration levels and extensive use of digital signal processing. However, the integration in standard CMOS of increasingly complex analog/RF parts imposes a number of challenges and trade-offs that make their design critical. These challenges are addressed in this paper through a comprehensive revision of the state-of-the-art on transceiver architectures, building blocks and design trade-offs of reconfigurable and adaptive CMOS RF and mixed-signal circuits for emerging 4G systems.

Highly Linear 2,5-V CMOS ΣΔ Modulator for ADSL+

We present a 90-dB spurious-free dynamic range sigma-delta modulator (/spl Sigma//spl Delta/M) for asymmetric digital subscriber line applications (both ADSL and ADSL+), with up to a 4.4-MS/s digital output rate. It uses a cascade (MASH) multibit architecture and has been implemented in a 2.5-V supply, 0.25-/spl mu/m CMOS process with metal-insulator-metal capacitors. The prototypes feature 78-dB dynamic range (DR) in the 30-kHz to 2.2-MHz band (ADSL+) and 85-dB DR in the 30-kHz to 1.1-MHz band (ADSL). Integral and differential nonlinearity are within /spl plusmn/0.85 and /spl plusmn/0.80 LSB/sub 14 b/, respectively. The /spl Sigma//spl Delta/ modulator and its auxiliary blocks (clock phase and reference voltage generators, and I/O buffers) dissipate 65.8 mW. Only 55 mW are dissipated in the /spl Sigma//spl Delta/ modulator.We present a 90-dB spurious-free dynamic range sigma-delta modulator M) for asymmetric digital subscriber line applications (both ADSL and ADSL ), with up to a 4.4-MS/s digital output rate. It uses a cascade (MASH) multibit architecture and has been implemented in a 2.5-V supply, 0.25- m CMOS process with metal-insulator-metal capacitors. The prototypes feature 78-dB dynamic range (DR) in the 30-kHz to 2.2-MHz band ADSL and 85-dB DR in the 30-kHz to 1.1-MHz band (ADSL). Integral and differential nonlinearity are within 0.85 and 0.80 LSB b , respectively. The modulator and its auxiliary blocks (clock phase and reference voltage generators, and I/O buffers) dissipate 65.8 mW. Only 55 mW are dissipated in the modulator.

Next-Generation Delta-Sigma Converters: Trends and Perspectives

This paper presents an overview of emerging circuits and systems techniques which are at the forefront of the state of the art in ΔΣ modulators, pushing their performance forward and giving rise to new generations of data converters. Among others, those strategies involving the development of new applications and paradigms-like RF/GHz-range ΔΣ digitisation, digital-assisted embedded loop filters, time-to-digital conversion and hybrid ΔΣ/Nyquist-rate architectures-are discussed, as well as the implications and design challenges derived from their integration in deep nanometer CMOS technologies. The envisioned ΔΣ techniques are presented in a systematic way around the main analog building blocks embedded in a ΔΣ modulator, i.e., the loop filter and the quantizer. Analysing the trends in the design of these blocks allows us to offer perspectives on how ΔΣ converters will evolve in the next years.

LC-Based Bandpass Continuous-Time Sigma-Delta Modulators With Widely Tunable Notch Frequency

This paper analyses the use of bandpass continuous-time ΣΔ modulators with widely programmable notch frequency for the efficient digitization of radio-frequency signals in the next generation of software-defined-radio mobile systems. The modulator architectures under study are based on a fourth-order loop filter - implemented with two LC-based resonators - and a finite-impulsive-response feedback loop in order to increase their flexibility and degrees of freedom. Several topologies are studied, considering three different cases for the embedded digital-to-analog converter, namely: return-to-zero, non-return-to-zero and raised-cosine waveform. In all cases, a notch-aware synthesis methodology is presented, which takes into account the dependency of the loop-filter coefficients on the notch frequency and compensates for the dynamic range degradation due to the variation of the notch. The synthesized modulators are compared in terms of their sensitivity to main circuit error mechanisms and the estimated power consumption over a notch-frequency tuning range of 0.1fs to 0.4fs. Time-domain behavioral and macromodel electrical simulations validate this approach, demonstrating the feasibility of the presented methodology and architectures for the efficient and robust digitization of radio-frequency signals with a scalable resolution and programmable signal bandwidth.

A 100kHz–10MHz BW, 78-to-52dB DR, 4.6-to-11mW flexible SC ΣΔ modulator in 1.2-V 90-nm CMOS

This paper presents an adaptive 1.2-V 90-nm CMOS cascade two-stage (2–2) SC ΣΔ modulator with 3-level quantization and unity signal transfer function in both stages. The chip reconfigures its loop filter order (either 2nd or 4th-order), clock frequency (from 40 to 240 MHz) and scales power according to the required specifications for different wireless standards, covering: GSM, Bluetooth, GPS, UMTS, DVB-H and WiMAX. Measurements feature a dynamic range of 78/70/71.5/66/62/52dB and a peak signal-to-(noise+distortion) ratio of 72.3/68.0/65.4/63.3 /59.1/48.7dB within 100kHz/500kHz/1MHz/2MHz/4MHz/10MHz, while consuming 4.6/5.35/6.2/8/8/11mW, respectively. These results show a competitive performance with the state-of-the-art multi-standard ΣΔ modulators, covering one of the widest regions in the DR-vs.-Bandwidth plane†1.

Dactylomelatriol, a biogenetically intriguing omphalane-derived marine sesquiterpene.

Dactylomelatriol (1), obtained from the sea hare Aplysia dactylomela, is the first naturally occurring omphalane-derived sesquiterpene from the marine environment. From this species the known chamigrene and modified bisabolene sesquiterpenes 2-6 were also isolated. The structure and relative configuration of 1 were established by spectroscopic evidence. Its chemical structure is related to omphalic acid, the unique terrestrial-derived omphalane sesquiterpene isolated from a liverwort. A biogenetic route for this compound is proposed. The antimicrobial activities of compounds 1-6 were evaluated against a panel of microorganisms.