Unique Regime Research Articles

Risk assessment of the Groningen geothermal potential: From seismic to reservoir uncertainty using a discrete parameter analysis

Geothermal exploitation is subject to several uncertainties, even in settings with high data availability, adding to project risk. Uncertainty can stem from the reservoir’s initial state, as well as from the geological and operational parameters. The interplay between these aspects entails irreducible risk prior to exploration drilling. Consequently it is difficult to construct an indicative qualitative and quantitative depiction of the most prominent facets (e.g. pressure, permeability). This paper shows the classification of known unknowns to risks, while also providing numerical results. Starting from seismic data and arriving at a reservoir model using a discrete parameter analysis we assess the risks and uncertainties of a geothermal project near the city of Groningen (NE Netherlands). By simulating all combinations of the considered parameters, their relative importance can be mapped out. Findings suggest that the unique regime of possible pressure depletion due to neighbouring gas production can highly impact the feasibility of the project. Results demonstrate how an in depth analysis at the exploration phase can direct future efforts towards the most significant elements. Although the numerical results are field specific, the methodology can be readily applied to different locations.

Precipitation Spectra Analysis Over China With High-Resolution Measurements From Optimally Merged Satellite/Gauge Observations—Part I: Spatial and Seasonal Analysis

Precipitation amount (PA), frequency (PF), and intensity (PI) over China are characterized and quantified using a high-resolution merged satellite-gauge precipitation product for 6 years (January 2008 through December 2013). The precipitation product synthesizes both state-of-the-art multisatellite precipitation algorithms and the latest, densest gauge observations to provide high-quality precipitation information at a very fine temporal and spatial resolution $(\text{0.1}^{\circ}\!/\text{hourly})$ that encompasses all of China. The geographical and seasonal variations in precipitation are systematically documented over seven subregions, each corresponding to a unique climate regime. PA, PF, and PI have large seasonal and geographical variations across China. It is found that 1) although heavy precipitation events $({ > } 10 \;\text{mm/h})$ represent only 0.8% of total precipitation occurrence over China, they contribute 12.1% of the total precipitation volume. Light precipitation events $({ dominate the precipitation occurrence (74.3%) and contribute 23.1% of the total precipitation volume; 2) over the high-altitude Tibetan Plateau (TP), the landlocked Xinjiang (XJ) province, and northwestern China (NW), light precipitation events $({ occur very frequently (74.7%, 82.1%, and 64.1% of all precipitation events) and contribute 29.8%, 35.5%, and 27.4% of the total precipitation volume. This initial continental-scale study provides new insights on precipitation characteristics that can benefit meteorological and hydrological modeling and applications, especially in areas with sparse rain-gauge coverage.

Internet Governance and the Jurisdiction of States: Justification of the Need for an International Regulation of Cyberspace

The issue of Internet governance is taking a forever more important place in the debate on the future shape of international society. Regarding the fact that national governments have decided to regulate the international cyberspace with state laws, it seems quite certain that the starting point for all considerations of Internet governance should be the analysis of the existing rules upon which the regulating states base their competences - the rules of international jurisdiction. The paper thoroughly discusses the traditional principles of international jurisdiction, shows their practical applications known so far and contrasts them with new circumstances, specific for the Internet, in which these rules should be used. It analyses the territoriality principle, effects principle, active and passive personality principle, protective principle and the universality principle. It discusses their use in traditional international law, including a brief look at the specific concept of international spaces with their unique jurisdictional regime. It than goes on to examine each of the discussed principles for their applicability to the Internet.The article presents also a brief look at the achievements done by international private law in the domain of international jurisdiction, as an invaluable source of experience from which the evolving cyberlaws should draw. Above all it points to the problems, encountered by private international law, bound with elaborating and applying international jurisdictional rules, that have to be analyzed in the context of cyber-activity, especially e-commerce and cybertorts.The solution to the present jurisdictional puzzle, proposed in the article, comprises of finding an international compromise on the scope of rules best suited for the cyber realm and, if applicable, elaborating their modifications. Such a compromise should become a part of an international agreement. The solution should constitute a new regime of Internet governance, elaborating it however is not possible without clearly setting out the basic rules of jurisdiction, that obviously must be altered to fit the evolving circumstances.

Tropical West Pacific moisture dynamics and climate controls on rainfall isotopic ratios in southern Papua, Indonesia

AbstractUnderstanding the controls on stable isotopologues of tropical rainfall is critical for paleoclimatic reconstruction from tropical ice core records. The southern Papua region, Indonesia, has a unique climate regime that allows for the evaluation of the influence of precipitation and convective activity on seasonal rainfall δ18O. The influence of the El Niño–Southern Oscillation (ENSO) on interannual rainfall δ18O variation is also important for paleoclimate reconstruction. Here we present stable isotope analyses of 1332 rain samples collected daily during the period from January 2013 to February 2014 (ENSO‐normal) and December 2014 to September 2015 (El Niño) at various elevation stations (9 to 3945 m above sea level) on the southern slope of the central mountain ranges in Papua. The results suggest an altitude effect with an isotopic lapse rate for δ18O (δD) of −2.4‰/km (−18.2‰/km). The temporal δ18O variability (daily to interannual) is controlled mostly by regional convective activity rather than local/regional precipitation amount. The intraseasonal δ18O variation resembles the Madden‐Julian Oscillation cycle with major δ18O depletion events associated with active (wet) phases. Moisture origins, transport pathways, moisture convergence, and raindrop evaporation appear to have no significant seasonal effects on δ18O, leading to the conclusion that condensation temperature controls δ18O depletion associated with convective activity. Seasonal δ18O variation is likely associated with atmospheric temperature at the mean condensation level as indicated by the altitude of latent heat release in the troposphere. Rainfall δ18O (δD) is generally enriched by 1.6‰–2‰ (11‰–15‰) during El Niño than during ENSO‐normal periods.

The implications of small stem cell niche sizes and the distribution of fitness effects of new mutations in aging and tumorigenesis.

Somatic tissue evolves over a vertebrate's lifetime due to the accumulation of mutations in stem cell populations. Mutations may alter cellular fitness and contribute to tumorigenesis or aging. The distribution of mutational effects within somatic cells is not known. Given the unique regulatory regime of somatic cell division, we hypothesize that mutational effects in somatic tissue fall into a different framework than whole organisms; one in which there are more mutations of large effect. Through simulation analysis, we investigate the fit of tumor incidence curves generated using exponential and power‐law distributions of fitness effects (DFE) to known tumorigenesis incidence. Modeling considerations include the architecture of stem cell populations, that is, a large number of very small populations, and mutations that do and do not fix neutrally in the stem cell niche. We find that the typically quantified DFE in whole organisms is sufficient to explain tumorigenesis incidence. Further, deleterious mutations are predicted to accumulate via genetic drift, resulting in reduced tissue maintenance. Thus, despite there being a large number of stem cells throughout the intestine, its compartmental architecture leads to the accumulation of deleterious mutations and significant aging, making the intestinal stem cell niche a prime example of Muller's Ratchet.

Dissolved organic carbon delivery from managed flow releases in a montane snowmelt river

Managed flow releases are increasingly being utilised in the rehabilitation of regulated rivers to improve physical habitat condition and restore spatial connectivity. However, the potential for managed flow releases to influence basal resource availability to the downstream food web has received less attention. This study investigated dissolved organic carbon (DOC) delivery from managed flow releases from Jindabyne Dam and a regulated tributary to the Snowy River; a mixed rainfall-snowmelt river in south-east Australia. DOC concentration and load were monitored downstream of Jindabyne Dam during two high-flow dam releases and 2 month-long tributary releases provided by temporarily suspending tributary weir diversions. DOC chemical composition in the downstream Snowy River was characterised using fluorescence spectrophotometry. A negligible change or decrease in DOC concentration occurred at all monitored sites during both dam releases. In contrast, pulsed increases in DOC concentration concomitant with natural high-flow events were observed in the Snowy River during the tributary releases. The estimated DOC load delivered by the larger dam release increased 1.5-fold between sites 2 and 22 km downstream of the Jindabyne Dam. Reservoir release waters contained both humic-like and protein-like DOC fluorophores, whereas tributary releases contained only humic-like DOC fluorophores. Collectively, these results suggest that changes in DOC quantity and composition during managed dam releases reflect localised wetting and DOC mobilisation from the riparian zone whilst tributary releases deliver storm-associated pulses of terrestrial DOC flushed from the catchment. The unique DOC regimes associated with dam and tributary-sourced water releases may influence ecosystem functioning in the downstream river.

Real world treatment patterns of previously treated advanced gastric and gastroesophageal junction adenocarcinoma (GC) in Mexico.

143 Background: Little evidence is available on the management of patients (pts) with advanced GC after 1st-line treatment (tx). Until recently, no licensed therapies for 2nd-line tx were available. This study presents real-world data on pts characteristics, tx patterns, and resource utilization for these pts in Mexico. Methods: Data from medical charts was collected from 3 centers (tertiary-level). Eligible pts were ≥ 18 years old, diagnosed Jan 2007 - Jan 2015 with advanced or metastatic GC, had received 1st-line fluoropyrimidine+platinum, had ≥ 3 months of follow-up after 1st-line discontinuation, and had not participated in a clinical trial. Data were summarized using descriptive statistics. Results: Data from 180 charts was collected; the majority from the Mexican Institute of Social Security (IMSS) (167; 92.8%). Pts' mean age was 57.2 (±12.4) years and 56.7% were male. ECOG performance status (PS) during 1st-line tx was 78.3% PS = 1, 17.2% PS = 2, 0% PS = 0. A total of 16 unique 1st-line regimes were identified, of which EOX (32.2%), XELOX (23.3%), and ECF (14.4%) were the most frequent. The most common reasons for discontinuation were completion of planned regimen (27.2%), toxicity (27.2%) and disease progression (16.7%). A total of 151 (83.9%) pts received 2nd-line chemotherapy. Of these, 54.3% were PS = 1 and 33.1% PS = 2. A total of 19 regimes were identified; with the most frequent being capecitabine (34.4%), docetaxel (16.6%), and XELOX (13.9%). Among pts who received 2nd-line chemotherapy, 50 (33.1%) received 3rd-line chemotherapy. Resource use for patients receiving 2nd-line chemotherapy was: pain interventions (7.3%), nutritional support (1.3%), radiotherapy (13.9%), transfusions (10.6%), inpatient care (15.2%), emergency room visits (2.0%) and outpatient visits (other than scheduled follow-up) (3.3%). Conclusions: This study shows considerable variation in chemotherapy regime in both 1st- and 2nd-line therapy of pts with advanced GC. Understanding GC tx patterns in Mexico will help address unmet needs. Limitations: Pts who did not receive 2nd-line tx are likely underrepresented because these pts are typically managed at local clinics and not tertiary hospitals.

Insight into the Evaporation Dynamics of a Pair of Sessile Droplets on a Hydrophobic Substrate.

In this work, we have demonstrated three unique regimes in the evaporation lifecycle of a pair of sessile droplets placed in variable proximity on a hydrophobic substrate. For small separation distance, the droplets undergo asymmetric spatiotemporal evaporation leading to contact angle hysteresis and suppressed vaporization. The reduced evaporation has been attributed quantitatively to the existence of a constrained vapor-rich dome between the two droplets. However, a dynamic decrease in the droplet radius due to solvent removal marks a return to symmetry in terms of evaporation and contact angle. We have described the variation in evaporation flux using a universal correction factor. We have also demonstrated the existence of a critical separation distance beyond which the droplets in the droplet pair do not affect each other. The results are crucial to a plethora of applications ranging from surface patterning to lab-on-a-chip devices.

A 14,000-year record of fire, climate, and vegetation from the Bear River Range, southeast Idaho, USA

The vegetation and fire history of the Bear River Range (BRR), Southeast Idaho has been reconstructed from pollen, plant macrofossils, and macroscopic charcoal from lacustrine sediments. Overall, the BRR record shows independent responses of vegetation and fire regime to climate variation. The reconstructions suggest strong seasonal bias from the proxies evaluated, with the pollen record most sensitive to insolation-driven summer temperature trends, and the charcoal-based fire record more sensitive to winter snowpack variability. Together, the proxies suggest that the early Holocene experienced larger than average snowpacks but very warm summers. Warmer than modern summer temperatures were maintained through much of the mid-Holocene, but snowpacks decreased dramatically, creating the most extreme xeric conditions in the Holocene between ~7100 and 6000 BP. After 6000 BP, summers began to show a consistent cooling trend. Winter precipitation remained low until ~4400 BP, after which higher than average snowpacks are indicated until 2000 BP. Pollen and charcoal data relationships at ~8800 BP and from 1800 to 800 BP suggest periods with anomalously wet summers that created a unique fire regime during those intervals.

Flow regime mapping of high inertial gas–liquid droplet microflows in flow-focusing geometries

Confined gas–liquid droplet microflows present a lot of new perspectives for microfluidic systems that require the presence of a gaseous phase. In addition to the benefits associated with the discretization of reactive and sensing processes, the highly inertial droplets generated in these systems can enable fast efficient mixing by pair collisions as well as high system throughput due to the short convective timescales involved in the droplet transport. Presented herein is mapping of the geometry-specific droplet generation from a binary gas–liquid flow for different flow-focusing configurations. The dynamic interactions of inertia, shear stress, viscous and surface tension forces create three unique regimes in the gas–liquid flow rate space, providing adaptable flow configuration to specific applications. Analytical investigation and numerical analyses involving governing forces are also introduced to predict the effective droplet diameter versus gas flow rate. We found that the experimental results were well matched to the analytical predictions within 10 % of uncertainty.

Weather extremes : A spatio-temporal perspectives

Being mainly an agricultural country the economy of India and its growth mainly depends on the vagaries of the weather and in particular the extreme weather events. India with a land of unique climatic regime due to several characteristic features, including (i) two monsoon seasons (south-west and north-east) leading to drought & flood condition, active and break cycle of monsoon and also heavy rainfall leading to flash flood and landslides, (ii) two cyclone seasons (pre and post-monsoon cyclone seasons), (iii) hot weather season characterized by severe thunderstorms, dust storms and heat waves, (iv) cold weather season characterized by violent snow storms in the Himalayan regions, cold waves and fog. The socio-economic impacts of the extreme weather events such as floods, droughts, heavy rainfall, cyclones, hail storm, thunderstorm, heat and cold waves have been increasing due to large growth of population and urbanizations, which has led to greater vulnerability. A spatio-temporal analysis of these weather extremes over India will be very helpful to understand the vulnerability potential and to improve the forecast skill and use these forecasts in minimizing the adverse impacts of such weather extremes.

Financing LNG infrastructure using master limited partnerships

In recent years, an unprecedented level of capital has been invested in developing Australia’s latest liquefied natural gas (LNG) projects, with several more still in the pipeline. In the wake of ever-increasing oil price volatility, and international competitiveness and uncertainty in the global financial markets, Australian LNG projects that are either under development or are being proposed continually face pressure to be more cost-efficient and value-accretive to their capital providers. The application of cutting-edge technology, such as floating LNG, together with more innovative financing strategies, are among the key factors that could provide more attractive project yields to make investing in new greenfield LNG projects more commercially viable. For many years, master limited partnerships (MLPs) have been used as a tax-effective financing vehicle in the North American energy and resources sector for funding the construction of gas infrastructure assets. This extended abstract explores the feasibility of holding Australian LNG infrastructure assets such as LNG pipelines and processing facilities within a MLP structure, including: how a typical MLP investment model would work in practice in the LNG sector; the fiscal treatment of a MLP and its impact on investor yield; the types of LNG assets that are appropriate for a MLP structure; the suitability of the MLP vehicle in the Australian context; commercial considerations in establishing and maintaining a MLP structure, including transactional costs and Australia’s unique Petroleum Resource Rent Tax regime; and, sustainability of the MLP model in the context of the current Australian and worldwide focus on fiscal accountability.

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging.

Micron-sized lipid-stabilised bubbles of heavy gas have been utilised as contrast agents for diagnostic ultrasound (US) imaging for many years. Typically bubbles between 1 and 8 μm in diameter are produced to enhance imaging in US by scattering sound waves more efficiently than surrounding tissue. A potential area of interest for Contrast Enhanced Ultrasound (CEUS) are bubbles with diameters <1 μm or 'nanobubbles.' As bubble diameter decreases, ultrasonic resonant frequency increases, which could lead to an improvement in resolution for high-frequency imaging applications when using nanobubbles. In addition, current US contrast agents are limited by their size to the vasculature in vivo. However, molecular-targeted nanobubbles could penetrate into the extra-vascular space of cancerous tissue providing contrast in regions inaccessible to traditional microbubbles. This paper reports a new microfluidic method for the generation of sub-micron sized lipid stabilised particles containing perfluorocarbon (PFC). The nanoparticles are produced in a unique atomisation-like flow regime at high production rates, in excess of 10(6) particles per s and at high concentration, typically >10(11) particles per mL. The average particle diameter appears to be around 100-200 nm. These particles, suspected of being a mix of liquid and gaseous C4F10 due to Laplace pressure, then phase convert into nanometer sized bubbles on the application of US. In vitro ultrasound characterisation from these nanoparticle populations showed strong backscattering compared to aqueous filled liposomes of a similar size. The nanoparticles were stable upon injection and gave excellent contrast enhancement when used for in vivo imaging, compared to microbubbles with an equivalent shell composition.

Mapping recent burned patches in Siberian larch forest using Landsat and MODIS data

Mapping burned area at relatively high spatio-temporal resolution is important to assess the causes and consequences of landscape fire in forest ecosystems. A simple algorithm, Burned Area Extraction and Dating (BAED) algorithm, was developed to automatically extract burned patches and determine approximate date of fire occurrence for each burned perimeter. Burned perimeters were extracted by a two stage approach, including determining “core burned” pixels and shape of the burned patches, from successive Landsat images. A time series model that has components of seasonality and trend was fitted from MODIS (MODerate-resolution Imaging Spectroradiometer) NDVI (Normalized Difference Vegetation Index) product. The approximate date of fire occurrence for each burned patch was assigned when the difference between the observed NDVI and the predicted NDVI from the time series model exceeded a threshold for three consecutive times. The BAED algorithm was tested in Siberian larch forest, an ecosystem with unique fire regime and considerable contribution to the global carbon balance. The results suggested that correct rate detected by BAED algorithm increases sharply when fire size < 200 ha, and then levels at 90% thereafter. The BAED provides ecologists an easy way to map burned area for assessing ecological effects of landscape fire in Landsat data poor regions.

Hydrogenation vs. H-D isotope scrambling during the conversion of ethylene with hydrogen/deuterium catalyzed by platinum under single-collision conditions.

The catalytic hydrogenation of olefins promoted by transition metals, represented here by the conversion of ethylene with platinum, was studied under a unique regime representing pressures in the mTorr range and single-collision conditions. Isotope labeling was used to follow the concurrent H-D exchange steps that occur during this conversion. Multiple isotope substitutions were observed in the resulting ethane products, reflecting the operability of the reversible stepwise mechanism proposed a long time ago by Horiuti and Polanyi. In fact, the ethane isotopologue distributions obtained in these experiments reflect a much higher probability for the dehydrogenation of ethyl intermediates back to the olefin, relative to the hydrogenation to ethane, than typically seen in this catalysis. In addition, a second mechanistic pathway was clearly identified, responsible for most of the dideuteroethane produced. Based on the dependence of the rates of formation of each isotopologue on the fluxes of deuterium and ethylene, it is argued that this second route may be a "reverse" Eley-Rideal step between gas-phase ethylene and two deuterium atoms adsorbed on adjacent sites of the platinum surface. The clear identification of this second pathway is new, and was possible thanks to our ability to explore a new single-collision intermediate pressure regime.

Experimental characterisation of two fully-developed enclosure fire regimes

This work revisits the principle characteristics of two unique regimes of behaviour of fully-developed compartment fires first identified during the immense body of research that came to define the compartment fire framework. Experimentation and computational modelling are used to explore, compare and contrast the characteristics of these two Regimes and identify the transition or break point between the two. Their relevance to the design of contemporary infrastructure and need for a greater understanding of both Regimes in this context is discussed.

Shear connection modelling for column removal analysis

Although methods for modelling steel shear connections under column removal scenarios are available in widely-used design guidelines, they tend to be based on earthquake engineering research rather than research examining scenarios relevant to progressive collapse. Even where these have been adapted explicitly for this new purpose, they take a form that does not account for the true connection behaviour under this unique loading regime. This paper describes an accurate mechanical model that has been developed based on observations from a comprehensive testing programme designed specifically to study the behaviour of steel shear connections under column removal scenarios. The model is used to assess the influences of key parameters and develop a simple single-spring model practical for use in full-building collapse analyses.

Siblings of the Dragon: China's Territories and Constitutional Law

China’s territories are asymmetrical. Ideologically, statist socialism remains the People’s Republic of China (PRC)’s orthodoxy, but Hong Kong retains a “free market” of speech and belief in accordance with the Basic Law of the Hong Kong Special Administrative Region (HKSAR). Societally, in China’s peripheries, ethnic minorities, as territorial majority groups, are entitled to preserve their languages and cultures in autonomous (administrative) regions. Only in China proper have ethnic Han Chinese retained demographic dominance. Constitutionally, the Chinese state is a hybrid of various constituent units – special administrative regions, ethnic autonomous regions, and others of diverse legal statues – the theoretically “unitary” nature is under questions. According to Chinese legend, a dragon can have nine siblings and each of them are different – one who loves music sits on a lute; another who has good eyes resides up on the roof. This article argues that the asymmetry of Chinese territories, like the differences among the dragon’s siblings, has set the Chinese territories apart from ordinary administrative divisions, and created a unique regime of jurisprudential significance. As a matter of scope, this article will explore only three phenomena. The first section addresses the heterarchy of authorities in the Chinese context. The PRC central government and the territories are neither of equal authority, nor do they form a heterarchy of authorities with the PRC central government at the top. Ordinary administrative divisions are subordinate to a central government, but the territories may vary in institutions, cultures, and political attachments. The second section goes to the relationship between the authorities and citizens/nationals. The PRC, as a theoretically unitary state, still does not offer homogenous citizenship to all Chinese nationals. In fact, Chinese nationals registering residentship in different jurisdictions are entitled to various rights and legal treatments; in many circumstances, Chinese nationals are neither citizens nor aliens in a Chinese territory. This, nevertheless, has much outstripped what ordinary administrative divisions are supposed to do. In the third section, the article addresses the territories’ relationship with the international community. The structure of this article may be understood as a tripartite covering the relationship between the territorial authorities and the PRC central government with territorial authorities, individuals and foreign states respectively. Hypothetically, a unitary state’s relationship, legal or political, with its citizens/nationals should be simple and direct. As modernist constitutionalism presumes, the constituent power shall vest in a singular “people” as the demos of a liberal democracy and the constituted power ought to be primarily provided by a single Constitution. However, as the following sections will illustrate, the Chinese cases obviously depart from this presumption.

Nonlinear effects in optical pumping of a cold and slow atomic beam

By photoionizing hyperfine (HF) levels of the Cs state $6{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around $180\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s})$ spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The evolution of population within the HF structure is calculated by numerical integration of the multilevel optical Bloch equations. The agreement between numerical results and experiment outcomes is excellent. All main features in the experimental findings are explained by the occurrence of ``dark'' and ``bright'' resonances leading to power-dependent branching coefficients.

The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels

The effect of Nb on the hardenability of ultra-thin cast strip (UCS) steels produced via the unique regime of rapid solidification, large austenite grain size, and inclusion engineering of the CASTRIP© process was investigated. Continuous cooling transformation (CCT) diagrams were constructed for 0, 0.014, 0.024, 0.04, 0.06 and 0.08 wt% Nb containing UCS steels. Phase nomenclature for the identification of lower transformation product in low carbon steels was reviewed. Even a small addition of 0.014 wt% Nb showed a potent effect on hardenability, shifting the ferrite C-curve to the right and expanding the bainitic ferrite and acicular ferrite phase fields. Higher Nb additions increased hardenability further, suppressed the formation of ferrite to even lower cooling rates, progressively lowered the transformation start and finish temperatures and promoted the transformation of bainite instead of acicular ferrite. The latter was due to Nb suppressing the formation of allotriomorphic ferrite and allowing bainite to nucleate at prior austenite grain boundaries, a lower energy site than that for the intragranular nucleation of acicular ferrite at inclusions. Strength and hardness increased with increasing Nb additions, largely due to microstructural strengthening and solid solution hardening, but not from precipitation hardening.