A 0.88pJ/bit 112Gb/s PAM4 transmitter is reported in 7nm FinFET CMOS with 1V ppd output amplitude. The quarter-rate TX architecture implements a 5-tap analog FFE using tap extension circuitry, which permits higher FFE tap count than conventional quarter-rate architectures without requiring complex clocking. A key feature of the FFE construction is the use of fully re-assignable CML driver segments among FFE taps, which allows a reduced number of segments for lower capacitance and higher driver bandwidth.

This article details the design and measurement of a digital-to-analog converter (DAC)-based source-series terminated (SST) transmitter (TX) for wireline applications in 4-nm FinFET CMOS technology. The DAC achieves 8-bit resolution and high analog output bandwidth by using a segmented architecture along with a single-ended LSB. Strength adjustment of the lower four DAC LSBs relative to the upper four DAC MSBs is accomplished with a hybrid analog/digital tuning approach, which overcomes minimum device-size limitations that can limit the effectiveness of pure digital tuning for SST drivers. The resulting DAC design achieves well-matched MSB/LSB segments with −0.63/0.67 LSB integral nonlinearity (INL) and −0.16/0.43 LSB differential nonlinearity (DNL). Time-domain modulation of 216-Gb/s PAM8 and frequency-domain modulation of 212-Gb/s orthogonal frequency-division multiplexing (OFDM) are reported, demonstrating the capability of CMOS DACs to support frequency-domain modulation for wireline applications. The TX consumes 288 mW from a 0.95-V power supply.

Aquatic ecosystems world-wide are being irreversibly altered, suggesting that new and innovative management strategies are necessary to improve ecosystem function and sustainability. In river ecosystems degraded by dams environmental flows and selective withdrawal (SWD) infrastructure have been used to improve habitat for native species. Yet, few studies have quantified nutrient and food web export subsidies from upstream reservoirs, despite their potential to subsidize downstream riverine food webs. We sampled nutrient, phytoplankton, and zooplankton concentrations in outflows from the Shasta-Keswick reservoir complex in Northern California over a 12-month period to understand how SWD operation and internal reservoir conditions interact to influence subsidies to the Sacramento River. We found that nutrients, phytoplankton, and zooplankton were continuously exported from Shasta Reservoir to the Sacramento River and that gate operations at Shasta Dam were important in controlling exports. Further, our results indicate that gate operations and water-export depth strongly correlated with zooplankton community exports, whereas internal reservoir conditions (mixing and residence time) controlled concentrations of exported zooplankton biomass and chlorophyll a. These results demonstrate that reservoirs can be an important source of nutrient and food web subsidies and that selective withdrawal infrastructure may provide a valuable management tool to control ecosystem-level productivity downstream of dams.

Species management and conservation efforts are often based on range-wide trends, assuming dynamic equilibrium across space and time, even though fine-scale variability may be driving local dynamics. Oncorhynchus mykiss is a globally introduced, facultatively anadromous salmonid that is experiencing demographic shifts characterized by greater proportions of population remaining in freshwater. The degree of niche overlap between age classes of O. mykiss in freshwater environments may dictate how resources are partitioned within populations. We conducted a meta-analysis of age-specific O. mykiss habitat use to evaluate the degree of niche-partitioning between age classes and how age-specific habitat use relates to global in-stream and landscape level habitat variation. O. mykiss used deeper habitats as they grew towards maturity but did not partition habitat based on water velocity or substrate composition. As annual precipitation increased, O. mykiss used deeper and shallower habitats, and as summer air temperature increased, O. mykiss used shallower habitats. O. mykiss of native origin used deeper habitats than nonnative O. mykiss. However, a large proportion (42–99%) of variation in habitat use was associated with study or ecoregion, making climactic predictors unreliable for predictive species distribution or population dynamics models. Although the exact mechanisms driving geographic variability in O. mykiss habitat use are not fully understood, our results boost our understanding of how demographic shifts affect population resilience under climate change. Further research incorporating individual competitive behavior in predictive population models may elucidate the links between resource availability, demographic rates, and long-term O. mykiss population stability.

A 56 GS/s 8-bit asynchronous SAR ADC fabricated in 4nm CMOS technology is demonstrated. The 16x4 interleaved ADC uses a novel bootstrapping technique and a class-AB follower in the 1 st rank interleaver. It achieves a broad input common-mode (CM) range; from 0.3V to 0.6V, the total harmonic distortion stays below -52dB at 4.1 GHz with -0.2dBFS amplitude at 0.8V PPD maximum full scale. The ADC includes analog foreground calibration means for offset, gain, skew, and bandwidth. The measured ENOB is 6.5 at low frequency and stays above 5.2 up to Nyquist frequency. The bandwidth is higher than 27 GHz. The ADC uses a single 0.8V supply voltage and achieves an efficiency of 47 fJ/conv.step.

A DAC-based SST transmitter for wireline applications is reported in a 4nm FinFET technology. 8b resolution and high analog output bandwidth (BW) are achieved by employing a segmented architecture along with a single-ended LSB. Hybrid analog/digital tuning is used in the DAC LSB segments, resulting in well-matched MSB/LSB segments with -0.63/0.67 LSB INL and -0.16/0.43 LSB DNL. 216Gb/s PAM8 and 212Gb/s QAM64 OFDM operation are demonstrated at 288mW from a 0.95V supply.

Monitoring is an essential component in ecosystem management, and leveraging existing data sources for multiple species of interest can be one effective way to enhance information for management agencies. Here, we analyzed juvenile Chinook Salmon (Oncorhynchus tshawytscha) bycatch data that has been collected by the recently established Enhanced Delta Smelt Monitoring program (EDSM), a survey designed to estimate the abundance and distribution of the San Francisco Estuary’s (estuary) endangered Delta Smelt (Hypomesus transpacificus). Two key aspects of the EDSM program distinguish it from other fish surveys in the estuary: a stratified random sampling design and the spatial scale of its sampling effort. We integrated the EDSM data set with other existing surveys in the estuary, and used an occupancy model to assess differences in the probability of detecting Delta Smelt across gear types. We saw no large-scale differences in size selectivity, and while detection probability varied among gear types, cumulative detection probability for EDSM was comparable to other surveys because of the program’s use of replicate tows. Based on our occupancy model and sampling effort in the estuary during spring of 2017 and 2018, we highlighted under-sampled regions that saw improvements in monitoring coverage from EDSM. Our analysis also revealed that each sampling method has its own benefits and constraints. Although the use of random sites with replicates, as conducted by EDSM, can provide more statistically robust abundance estimates relative to traditional methods, the use of fixed stations and simple methods such as beach seining may provide a more cost-effective way to monitor salmon occurrence in certain regions of the estuary. Leveraging the strengths of each survey’s method can enable stronger inferences on salmon abundance and distribution. Careful consideration of these trade-offs is crucial as the management agencies of the estuary continue to adapt and improve their monitoring programs.

Resource managers rely on large-scale flow and habitat enhancement actions to support sensitive species in the San Francisco Bay-Delta. The effects of these actions on target species and ecosystems are largely unknown. In 2018, we implemented an ecosystem-scale experiment to reduce salinity and improve access to high-quality habitat in Suisun Marsh, California, for Endangered Species Act-listed Delta Smelt Hypomesus transpacificus. The action included a release of approximately 46 million m(3) of additional flow in conjunction with the operation of a novel water management facility, the Suisun Marsh Salinity Control Gates. This experimental action resulted in more low-salinity habitat in Suisun Marsh than would have been present as compared to similar historical low-flow summer conditions. We evaluated the effect of decreasing salinity on the species assemblage in Suisun Marsh using a combination of ordination analyses and circular statistics. We focused this analysis on long-term monitoring data collected within Suisun Marsh during July and August and found that the aquatic community changed significantly in small sloughs but not large-slough habitat in response to the Suisun Marsh action. The assemblage shift from July to August 2018 differed from historical trends in both slough sizes, albeit not significantly in large-slough habitat. Specifically, we observed (1) a shift in California bay shrimp Crangon franciscorum and Striped Bass Morone saxatilis abundance like that occurring in low-salinity, wet water year types; and (2) an uncharacteristic seasonal decline in Black Sea jellyfish Maeotias marginata. We posit that the observed community changes were driven by a combination of behavioral responses to lower-salinity conditions and physical displacement by directional flow resulting from the flow management action.

While flow is known to be a major driver of estuarine ecosystems, targeted flow manipulations are rare because tidal systems are extremely variable in space and time, and because the necessary infrastructure is rarely available. In summer 2018 we used a unique water control structure in the San Francisco Estuary (SFE) to direct a managed flow pulse into Suisun Marsh, one of the largest contiguous tidal marshes on the west coast of the United States. The action was designed to increase habitat suitability for the endangered Delta Smelt Hypomesus transpacificus, a small osmerid fish endemic to the upper SFE. The approach was to operate the Suisun Marsh Salinity Control Gates (SMSCG) in conjunction with increased Sacramento River tributary inflow to direct an estimated 160 x 106 m3 pulse of low salinity water into Suisun Marsh during August, a critical time period for juvenile Delta Smelt rearing. Three-dimensional modeling showed that directing additional low salinity water into Suisun Marsh ("Flow Action") substantially increased the area of low salinity habitat for Delta Smelt that persisted beyond the period of SMSCG operations. Field monitoring showed that turbidity and chlorophyll were at higher levels in Suisun Marsh, representing better habitat conditions, than the upstream Sacramento River region throughout the study period. The Flow Action had no substantial effects on zooplankton abundance, nor did Suisun Marsh show enhanced levels of these prey species in comparison to the Sacramento River. Fish monitoring data suggested that small numbers of Delta Smelt colonized Suisun Marsh from the Sacramento River during the 2018 Flow Action. Comparison of the salinity effects of the Flow Action to historical catch data for Suisun Marsh further supported our hypothesis that the Flow Action would have some benefit for this rare species. Our study provides insight into both the potential use of targeted flow manipulations to support endangered fishes such as Delta Smelt, and into the general response of estuarine habitat to flow management.

We report on efforts to develop a high speed, low cost, low energy chip scale optical module for co-packaging on a first-level organic substrate for HPC and Data Center applications.

In the above-named work, the photograph that appeared next to the author, Herschel A. Ainspan, was not an image of this author and was published in error. No photo should have accompanied his name.

The ever-increasing demand for higher bandwidth continues to fuel the need for faster and more power-efficient IOs, with the next generation high-speed serial links expected to reach data rates higher than 112Gb/s using PAM-4 signaling [1–3]. While PAM-4 spectral efficiency is better than that of NRZ, it is less tolerant of residual ISI and noise. As a consequence, a driver with high bandwidth and large output amplitude is required. This paper presents a 64Gbaud PAM-4 TX with a fully reconfigurable 3-tap FFE, which achieves a power efficiency of 1.3pJ/b in PAM-4 mode and 2.7pJ/b in NRZ mode for a differential output swing of $1\mathrm{V}_{ppd}$. A feature of the FFE construction is the use of fully re-assignable FFE segments among the 3 taps, which allows a reduced number of segments for lower capacitance and higher driver bandwidth. To minimize power consumption, a quarter-rate clocking architecture is adopted with a tailless 4:1 multiplexer, which also acts as a pre-driver to a tailless CML output driver.

Gravel augmentation is often applied to rivers and streams to rehabilitate salmonid spawning and incubation habitat. However, the effect of gravel size on salmon spawning utilization and embryo survival during incubation is not well understood. We conducted an experiment on a regulated and previously mined Northern California salmonid‐bearing stream in which different sized gravel (small, medium, and large) patches were placed into the stream's degraded spawning reach. We documented Oncorhynchus tshawytscha (Chinook salmon) spawning activity within the three gravel sizes for two seasons. In addition, we deployed Chinook salmon embryos into each gravel size patch and allowed them to incubate until estimated emergence time. Although all experimental gravel sizes were predicted to be within the spawning population's mobilization capabilities, model results indicated the probability of salmon building redds decreased as substrate size increased. Conversely, embryo survival increased as gravel size increased. A possible mechanism of disparate Chinook salmon embryo survival is provided by an observed decrease in embryo survival correlating with greater presence of embryo predators (leeches), which are associated with smaller gravel. Our results indicate a parent‐offspring conflict in optimal spawning gravel size for Chinook salmon, and suggest that an intermediate gravel size would maximize overall reproductive success across both spawning and incubation life stages.

Abstract Association with physical structure or conspecifics can impact individual growth and survival. The necessity and strength of these associations changes with environmental conditions and ontogeny, acting in concert or opposition to influence an individual's behavior and ultimate success. We conducted a field experiment on the San Joaquin River, California, with juvenile Chinook salmon (Oncorhynchus tshawytscha) to test hypotheses related to the impacts of physical structure proximity and environmental and ontogenetic change on aggregating behavior of a migratory fish. We created orthogonal combinations of structural cover, turbidity, and juvenile Chinook salmon size and density by manipulating the location of artificial structure within net pens at three sites along the lower river and recorded observations of juvenile salmon swimming in aggregations with underwater video cameras. We selected the most parsimonious generalized linear mixed effects model via Akaike Information Criteria to analyze the effects of structure proximity, turbidity, and salmon size and density on aggregating behavior. The proportion of our observations composed of fish in aggregation increased significantly when fish were >3.5 m from structure; the strength of this effect declined significantly as turbidity, fish length, or fish density increased. We observed a significant decline in aggregation behavior when turbidity increased from 0.5 to 8.5 NTU and fish were more than 3.5 m from physical structure. Turbidity had minimal impact on behavior of fish within 1 m of structure. The proportion of our observations composed of fish in aggregation increased significantly when mean fish fork length increased from 45 mm to 80 mm, or fish density increased from ~0.2 n/m2 to 3.5 n/m2. Collectively, these results highlight how changes in the physical environment (i.e., structure and turbidity) and ontogeny interactively affect the frequency at which juvenile salmon swim in aggregation.

As CMOS devices continue to scale down in voltage and area, digital-based high-speed serial I/Os [1] become increasingly competitive with analog-based designs [2,3]. In addition to offering the PVT-independent performance of digital functions and superior power and area scaling to future technology nodes, digital-based I/Os can support advanced line modulation techniques that will become necessary as long-reach electrical channel data rates scale to 56Gb/s and beyond. The key enablers of a digital receiver are power and area efficient analog to digital conversion (ADC) and digital channel equalization. This paper describes the design of a 25Gb/s 2-level digital serial line receiver including a ¼-rate 5b flash ADC, an 8-tap feed-forward equalizer (FFE), an 8-tap decision-feedback equalizer (DFE), and a baud-rate clock and data recovery circuit (CDR). The receiver features a flash ADC, which employs a new power and area efficient slicer design capable of achieving high-precision (∼1mV) threshold accuracy with an associated on-chip calibration system. The 32nm SOI CMOS receiver achieves error-free operation with margin on a reflective transmission-line channel with 40dB half-baud loss.

The new era of cognitive computing brings forth the grand challenge of developing systems capable of processing massive amounts of noisy multisensory data. This type of intelligent computing poses a set of constraints, including real-time operation, low-power consumption and scalability, which require a radical departure from conventional system design. Brain-inspired architectures offer tremendous promise in this area. To this end, we developed TrueNorth, a 65 mW real-time neurosynaptic processor that implements a non-von Neumann, low-power, highly-parallel, scalable, and defect-tolerant architecture. With 4096 neurosynaptic cores, the TrueNorth chip contains 1 million digital neurons and 256 million synapses tightly interconnected by an event-driven routing infrastructure. The fully digital 5.4 billion transistor implementation leverages existing CMOS scaling trends, while ensuring one-to-one correspondence between hardware and software. With such aggressive design metrics and the TrueNorth architecture breaking path with prevailing architectures, it is clear that conventional computer-aided design (CAD) tools could not be used for the design. As a result, we developed a novel design methodology that includes mixed asynchronous-synchronous circuits and a complete tool flow for building an event-driven, low-power neurosynaptic chip. The TrueNorth chip is fully configurable in terms of connectivity and neural parameters to allow custom configurations for a wide range of cognitive and sensory perception applications. To reduce the system's communication energy, we have adapted existing application-agnostic very large-scale integration CAD placement tools for mapping logical neural networks to the physical neurosynaptic core locations on the TrueNorth chips. With that, we have successfully demonstrated the use of TrueNorth-based systems in multiple applications, including visual object recognition, with higher performance and orders of magnitude lower power consumption than the same algorithms run on von Neumann architectures. The TrueNorth chip and its tool flow serve as building blocks for future cognitive systems, and give designers an opportunity to develop novel brain-inspired architectures and systems based on the knowledge obtained from this paper.