Structural Change Research Articles

RF magnetron sputtering of [formula omitted] thin films: Analysis of thermal annealing induced tuning of structural, optical characteristics, and energy band alignments

This correspondence showcases the deposition of ultra-wide bandgap β−Ga2O3 thin films via the utilization of RF magnetron sputtering at an elevated deposition temperature of 400 °C, followed by a comprehensive analysis of their structural, surface and optical properties using X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Raman, Ultraviolet–Visible Spectroscopy (UV–Vis), and Atomic Force Microscopy (AFM) at 800 °C, 900 °C, and 1000 °C annealed sample. Annealing up to 1000 °C led to a significant enhancement in the film’s crystallinity by 10%, accompanied by a remarkable decrease in dislocation density of up to 93.5%. The study also observed several key trends upon annealing, including a decreasing lattice constant from 12 to 11.97 Å, and an increase in the bandgap from 4.8 to 5.3 eV. Concurrently, crystallite size was consistently increased from 4.07 to 15.77 nm. The conduction band offset (CBO) decreased with higher annealing temperatures. Additionally, the increase in bandgap led to an enhancement in the critical electric field from 8.9 to 11.2 MV/cm. The Electron Density Mapping (EDM) results depicted a covalent bond between the atoms for different annealing processes along with the fundamental structural change in atomic coordinates and unit cell parameters, which has not been reported yet. These findings underline the remarkable material properties of β−Ga2O3 at 1000 °C temperatures. This establishes it as a compelling substitute for materials like SiC and GaN, showcasing its potential across various high-power applications due to a superior Baliga figure of merit and robust sensitivity even under elevated temperatures, positioning it as a promising candidate for optoelectronic applications.

Behind the scenes of industrial change – Change agency and system function linkages

ABSTRACT Green transformation of industry and society is high on the research and policy agenda. The article presents a proposal for a theoretical framework for studying technological change based on the employment of system functions drawn from the literature on technological innovation systems in conjunction with existing theorisation on regional restructuring and change agency. The empirical focus of this article is on the Grenland region in Norway, a thick and specialised region that focuses on the ‘greening’ of traditional industries. The empirical data were gathered through an in-depth case study of the ongoing restructuring process in Grenland and further by adopting a path tracing methodological approach building on interviews held with key actors, in addition to desk research. The findings revealed how the restructuring process in Grenland can be broken down and understood by empirically examining links between different types of change agency and the utilisation of system functions. The author concludes that the findings provide important insights into the theoretical debate on how agency on a micro-level relates to institutional evolution and structural change.

Chiral recognition without π−π-interactions: Highly efficient chiral strong cation exchangers lacking an aromatic unit in the molecular structure

Current state-of-the-art chiral stationary phases (CSPs) enable chiral resolution of almost any racemic mixture of choice. The exceptions represent ionizable and ionized substances that fail at any attempts to resolve on commercially available CSPs. These compounds, however, can be efficiently separated on chiral ion exchangers. Commercially available Cinchona alkaloids-based chiral weak ion-exchangers are typically used for chiral resolution of organic acids, while zwitterion ion-exchangers are efficient in the resolution of acids, bases, and zwitterions. The latter possess in their structure a cation exchange unit, which alone can serve as a cornerstone of chiral strong cation exchangers facilitating chiral separation of various basic racemic mixtures.Although chiral strong cation exchangers (cSCX) are efficient CSPs, their structural variations have not been thoroughly studied so far. It was assumed that the mechanism of chiral recognition of basic compounds by cSCX is based predominantly on π-π-interactions, hydrogen bonding and steric interactions (CSP I). To verify this assumption, we aimed in our study on the design and synthesis of cSCX first lacking lateral polar substituents on the aromatic unit in the selector's structure (CSP II), and second, to replace the aromatic unit by a cyclohexane ring (CSP III and IV), thereby to omit completely the π-π-interactions. We hypothesized that this structural change should lead to a partial or complete loss of enantiorecognition power of the selectors. Surprisingly, the non-aromatic cSCXs have shown chiral recognition capability comparable to that of previously described chiral cation exchange-type CSPs: from 16 analytes screened, 11 analytes were baseline resolved and 5 partially resolved on CSP I, while non-aromatic CSP III resolved 10 analytes baseline and 6 partially.We discuss the structural motifs of the known cSCX and the novel non-aromatic selectors in a relationship with their chromatographic performance using a set of basic analytes. Moreover, we present a theory of an effective chiral recognition mechanism by two novel non-aromatic cSCXs based on the chromatographic results and quantum mechanical calculations.

Correlating structure and activity of pepsin enzyme in H2O and D2O for the study of gastric digestion

D2O, an isotope of H2O, is commonly used as a solvent in neutron scattering; the large difference in scattering length density between H and D can provide better contrast between the sample and the solvent. However, this is of concern for studies using enzymes as the use of D2O can influence protein interactions (due to differences in hydrogen bonding) and is therefore expected to affect the function, activity and solubility of enzymes. Neutron-based in vitro digestion assays on proteins, including those found in food or as oral protein and peptide drugs, often involve different solvents or pH conditions where the activity of the digestive enzyme may not be optimal. Herein, we investigate the structure and activity of the main gastric protease, porcine pepsin, in both H2O and D2O at pH values in the range 1 – 8. We showed that the activity of pepsin was lower in D2O, although the relative change in activity with pH was similar for both solvents. We demonstrated using a combination of SAXS and CD that this relative change in activity was not related to any structural change within the protein but was, rather, linked to relative changes in solubility of the protein.

The role of carboxylate ligand orbitals in the breathing dynamics of a metal-organic framework by resonant X-ray emission spectroscopy.

Metal-organic frameworks (MOFs) exhibit structural flexibility induced by temperature and guest adsorption, as demonstrated in the structural breathing transition in certain MOFs between narrow-pore and large-pore phases. Soft modes were suggested to entropically drive such pore breathing through enhanced vibrational dynamics at high temperatures. In this work, oxygen K-edge resonant X-ray emission spectroscopy of the MIL-53(Al) MOF was performed to selectively probe the electronic perturbation accompanying pore breathing dynamics at the ligand carboxylate site for metal-ligand interaction. It was observed that the temperature-induced vibrational dynamics involves switching occupancy between antisymmetric and symmetric configurations of the carboxylate oxygen lone pair orbitals, through which electron density around carboxylate oxygen sites is redistributed and metal-ligand interactions are tuned. In turn, water adsorption involves an additional perturbation of π orbitals not observed in the structural change solely induced by temperature.

Crystal structure analysis of the adduct 1:1 hexamethylenetetramine and succinic acid (HMT−C4) as a function of the temperature

Co−crystals of hexamethylenetetramine [N4(CH2)6, (HMT)] and dicarboxylic acids of general formula HOOC(CH2)n−2COOH with 4 ≤ n ≤ 14 (Cn), called HMT−Cn, exhibits structural properties strongly dependent on the length of the dicarboxylic acid chain, showing a wide variety of thermotropic phase transition sequence. This study focuses on describing the structural features of the HMT−C4 (1:1) adduct, a co-crystal of HMT and succinic acid (C4), exhibiting a reversible first-order phase transition at 222(4)K, as evidenced by differential scanning calorimetry (DSC) experiments. In contrast to a prior investigations , which did not identify this phase transition, our comprehensive temperature-dependent analysis, incorporating single crystal X-ray diffraction and DSC experiments, reveals a reversible structural change in the HMT−C4 (1:1) adduct structure upon cooling and heating. The crystal structures of the different observed phases are discussed in detail, emphasizing the role of O−H···N intermolecular hydrogen bonds in maintaining the connectivity between HMT and C4 molecules. The observed phase transition involves doubling the unit cell volume and significant reorientation of the −COOH groups at the end of the C4 chain at around 222(4)K. Our findings underscore the importance of additional temperature-dependent experiments, such as DSC, in avoiding erroneous structure modeling due to symmetry changes during temperature variations. The preservation of the acidic character of the C4 dicarboxylic chain throughout the temperature range adds additional insights to the understanding of the structural behavior of all the HMT−Cn (1:1) adducts.

Vegetation Productivity Slowdown on the Tibetan Plateau Around the Late 1990s

AbstractTibetan Plateau (TP) has experienced a slowdown of the vegetation greening since the late 1990s. This structural change (i.e., greening) along with canopy physiology (i.e., potential photosynthetic productivity) regulates vegetation gross primary productivity (GPP). However, it remains unclear how the joint regulation influences the trend of alpine GPP under climate change. Here, we validate a universal productivity model against flux‐based and satellite‐derived observations at TP and diagnose the long‐term climatic impacts on GPP via canopy physiology and structure. We found an increasing but weakening trend of GPP after 1998. About 3/4 of this slowdown was attributed to the slowing greening after 1998, which was caused by the fact that the stress of atmospheric aridity and reduced benefits of warming overwhelmed the positive effects of CO2 fertilization and radiation enhancement. This study highlights the coupling between canopy structure and productivity for the long‐term period.

Manganese PNN pincer complex for hydrogenation of carbamate and urea derivatives: Reaction mechanism examined by DFT calculations

A comprehensive computational study is reported here on the mechanism of the reaction through which a Mn(I) pincer catalyst is able to assist the hydrogenation process of carbamate and urea derivatives, chosen as representative linker units of polyurethanes. Four substrate models, carbamate and urea derivatives, have been examined in order to evaluate their influence on the hydrogenation mechanism of polyurethanes to generate useful alcohols and amines organic building blocks. The outcomes of the computational exploration highlight a different behavior of the catalyst in assisting hydrogenation of carbamate or carbamide derivatives in the different steps of the whole reaction mechanism. Indeed, for the first hydrogenation step, the viability of a ligand-assisted mechanism has been found only for carbamide derivatives and involves a reversible structural change of the pincer ligand that can partially detach from the metal to favor the coordination of the molecule to be processed. The carbamate derivatives, instead, go through the formation of an intermediate in which the substrate interacts with the complex without binding. The mechanism of second hydrogenation is common to all the examined cases and requires the exploitation of the hemilabile nature of the PNN ligand. From the calculated energies put into play it clearly appears the great ability of the Mn(I) complex in catalyzing the hydrogenation of both carbamate and carbamide derivatives.

Atomic ordered doping leads to enhanced sensitivity of phosgene gas detection in graphene nanoribbon: a quantum DFT approach

We explore a novel sensor for detection of phosgene gas by graphene derivatives such as pristine and doped graphene nanoribbons via first principles calculations. The interaction of phosgene molecule with various edge and center doped configurations of boron, phosphorus and boron-phosphorus co-doped armchair graphene nanoribbon (AGNR) and zigzag graphene nanoribbon (ZGNR) is investigated through density functional theory (DFT). P-doped systems showcase chemisorption, displaying enhanced sensitivity to phosgene detection as reflected by a more negative adsorption energy values, accompanied by a prominent charge transfer due to the doping. Regardless of nanoribbon geometry, the binding energies of P-doped systems exhibit notable uniformity within the range of −8.01 eV to −8.49 eV, however the adsorption energies in ZGNR are significantly lower than those observed in AGNR. Due to much higher(lower) electron-donating (accepting) capacity of phosphorous(boron) atoms in comparison to ‘C’ atom, substitutional doping with ‘P’ or ‘B’ atoms in AGNR has signifiant impact on the structural, electronic and adsorption properties of the nanoribbons. We observe that phosphorus doped configurations (edge/center) effectively interact with phosgene molecule with higher adsorption that corresponds to the chemisorption phenomenon. The strongest adsorption energy (−8.83 eV) is obtained for P doped configurations, followed by that for B+P co-doped AGNR (−4.23 eV). These results suggest significantly stronger adsorption of phosgene gas on P doped AGNR than on any other systems reported so far. Band structure analysis estimates that by phosphorus doping, changes in the band gap is significant and it also shows prominent changes in the band structures. Isosurface electronic charge density plots identify that the transfer of charge takes place from graphene system to phosgene molecule. Thus, significant variation in adsorption and electronic properties of P doped AGNR reveal that these geometries immensely promote the detection of phosgene gas, and may be considered as promising chemical sensor for phosgene removal.

The plague, the skill-premium, and the road to modern economic growth

Abstract When bubonic plague arrived in Britain in the mid-14th century, it caused dramatic economic and structural change. Within 50 years, the skill-premium was reduced by half, and another 50 years on, agriculture’s share of the labor force had declined by more than 20 percentage points. This paper develops a two-sector pre-industrial growth model and draws on recent data sources covering Late Medieval and Early Modern Britain to explain these and the ensuing developments. Our main findings are that the skill-premium’s decline was related to the guild and apprenticeship system and that it and the other post-Plague adjustments were crucial determinants of the British trajectory toward industrialization. In particular, prior sectoral transformation and the skill-premium’s determination were important when the Early Modern population boom (1525–1654) threatened to reverse the adjustments caused by the Plague.

Structural phase transition and resistive switching properties of Cu x O films during post-thermal annealing

We studied the phase change and resistive switching characteristics of copper oxide (Cu x O) films through post-thermal annealing. This investigation aimed to assess the material’s potential for a variety of electrical devices, exploring its versatility in electronic applications. The Cu x O films deposited by RF magnetron sputtering were annealed at 300, 500, and 700 °C in ambient air for 4 min by rapid thermal annealing (RTA) method, and then it was confirmed that the structural phase change from Cu2O to CuO occurred with increasing annealing temperature. Resistive random-access memory (ReRAM) devices with Au/Cu x O/p+-Si structures were fabricated, and the ReRAM properties appeared in CuO-based devices, while Cu2O ReRAM devices did not exhibit resistive switching behavior. The CuO ReRAM device annealed at 500 °C showed the best properties, with a on/off ratio of 8 × 102, good switching endurance of ∼100 cycles, data retention for 104 s, and stable uniformity in the cumulative probability distribution. This characteristic change could be explained by the difference in the grain size and density of defects between the Cu2O and CuO films. These results demonstrate that superior and stable resistive switching properties of RF-sputtered Cu x O films can be obtained by low-temperature RTA.

Doing Community and Institutionally Engaged Work and Promoting Immigrant Well-being While Building a Research Career

This article offers reflections on doing community and publicly engaged research and scholarly work that promotes immigrant well-being while developing a research career in academic institutions which do not usually recognize or reward such work. I draw on my own career (as the editors asked me to do), and hope the advice or examples are helpful, especially to younger scholars. I write as a scholar who was not from the immigrant communities with which he worked, and who believes scholars should help create a society that respects the rights, dignity, and well-being of its members, especially immigrant families. I applaud the Im/migrant Well-being Scholar Collaborative initiative’s (IWSC or Collaborative) focus on immigrant well-being, which affirms not only work that seeks to make structural or policy change or to change debates (common foci of academic analysis), but also work that directly helps others, builds community capacity, or mentors broadly. I have tried to both promote well-being and to fight injustice and inequality.

Effect of glycation-induced concentration-dependent change in albumin structure and alteration in its binding capacity

Reducing sugars causes confirmatory alterations in albumin structure by the nonenzymatic glycation of the amino group of serum albumin. In this study, glucose and its hazardous metabolic products like glyoxal and methylglyoxal were incubated with bovine serum albumin (BSA). The confirmational changes in BSA molecule’s structure by glycating substances was investigated using a variety of spectroscopic methods, including deconvolutionFourier Transform Infra-red (FT-IR) spectroscopy, fluorescence spectroscopy, UV spectroscopy and circular dichroism (CD) spectroscopy. Dynamic fluorescence quenching was observed in the case of glucose, while static quenching was observed in the case of methyl glyoxal and glyoxal. Similarly, employing deconvolution FT-IR spectroscopy and CD spectroscopy for determination of change in secondary structures in terms signature of α-helix, β-turn, β-sheet and random coil modifications. Destabilization or unfolding of the albumin structure, due to the disruption of the hydrogen bonding pattern that stabilizes the albumin manifold, causes a 25-50% reduction in α-helix and a 2-fold increase in β-sheet and turns in glycated BSA. The competitive displacement interaction studies with warfarin were performed using the ultrafiltration technique and quantitative determination of free drug in ultrafiltrate using LC-MS/MS. The binding of carbamazepine (CBZ) or its active metabolite to proteins was unaffected by the glycation of BSA with glucose and methyl glyoxal. Nevertheless, with glyoxal-modified BSA, it changed the binding of selected analytes significantly. Based on in vitro observations and results, it could be anticipated that the serum CBZ concentration variation may be worsened in uncontrolled diabetes circumstances, with an overall variance of 30–40% possible. Communicated by Ramaswamy H. Sarma

Midfoot width changes after first metatarsal osteotomy in hallux valgus surgery: A biomechanical effect?

Hallux valgus is a challenging pathology characterized by a valgus deformity in the metatarsophalangeal area of the first ray. The aim of this study was to analyze the influence of first metatarsal osteotomy on the relationship between midfoot bones in patients with hallux valgus. The sample consisted of patients from the orthopedics and traumatology outpatient clinic who underwent surgical treatment for hallux valgus. Preoperative and postoperative X-rays were compared regarding the width of the midfoot and the tarsometatarsal joint. The sample consisted of 17 women, with 22 feet assessed in each group. The distance from the medial cuneiform to the cuboid, the distance from the intermediate cuneiform to the cuboid, the distance between the first and fifth metatarsals, and the distance between the second and fifth metatarsals reduced significantly between pre- and postoperative assessments. Hallux valgus correction through osteotomy of the first metatarsal leads to a structural change in the midfoot. Further studies should determine whether these changes persist over time.

Soldiers, civilians, and supply: lessons from Sevastopol

This article examines the supply crisis in Sevastopol during the Crimean War as a case study of war, economy, and society. Evidence shows that structural change and policy developments, rather than a technology deficit, produced systemic shortages across the Russian Empire. The resulting supply crisis on the battlefield spread from the military through the home front, and back again. Protests erupted as hungry soldiers and civilians sought scapegoats in vulnerable social groups. A new suspicion of internal enemies connected to supply networks emerged, and lasted into the Soviet era. While many aspects are unique to the Russian and Ukrainian historical experience, the potential social threat inherent to military supply remains universal.

A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings.

Olfactory dysfunction (OD) is one of the most common symptoms in COVID-19 patients and can impact patients' lives significantly. The aim of this review was to investigate the multifaceted impact of COVID-19 on the olfactory system and to provide an overview of magnetic resonance (MRI) findings and neurocognitive disorders in patients with COVID-19-related OD. Extensive searches were conducted across PubMed, Scopus, and Google Scholar until 5 December 2023. The included articles were 12 observational studies and 1 case report that assess structural changes in olfactory structures, highlighted through MRI, and 10 studies correlating the loss of smell with neurocognitive disorders or mood disorders in COVID-19 patients. MRI findings consistently indicate volumetric abnormalities, altered signal intensity of olfactory bulbs (OBs), and anomalies in the olfactory cortex among COVID-19 patients with persistent OD. The correlation between OD and neurocognitive deficits reveals associations with cognitive impairment, memory deficits, and persistent depressive symptoms. Treatment approaches, including olfactory training and pharmacological interventions, are discussed, emphasizing the need for sustained therapeutic interventions. This review points out several limitations in the current literature while exploring the intricate effects of COVID-19 on OD and its connection to cognitive deficits and mood disorders. The lack of objective olfactory measurements in some studies and potential validity issues in self-reports emphasize the need for cautious interpretation. Our research highlights the critical need for extensive studies with larger samples, proper controls, and objective measurements to deepen our understanding of COVID-19's long-term effects on neurological and olfactory dysfunctions.

Are we really addressing the roadblocks to adoption of renewable and sustainable energy technologies? Total interpretive structural modeling approach.

Urban areas serve as a vital contribution to the global structural change towards renewable and sustainable energy technologies which also influence climate change. The aim of this paper is to identify the adoption roadblocks to renewable and sustainable urban energy technologies. This research has three parts: a mini-systematic literature study was conducted to identify the most prevalent roadblocks. Using total interpretive structural modeling (ISM), the relationships between the roadblocks and the source of causation were then examined. The roadblocks are classified based on their dependence and driving powers using MICMAC analysis in the third part of this research. The principal results and major conclusions demonstrate that all roadblocks are necessary for renewable and sustainable urban energy technologies. The roadblocks at level I are insufficient infrastructure, lack of coordination among authorities, lack of quality and reliable data and information, and competition with non-renewable technologies; roadblocks in level II are lack of skilled and trained personnel, limited public participation, awareness, and consumer interest, and lack of standardized technology; roadblock in level III is high initial investment cost; and lastly, roadblocks in level IV are lack of subsidies and financial support programs and absence of coherent related policies. Furthermore, as a result of theMICMAC analysis, none of the aforementioned roadblocks are classified as autonomous variables, implying that they are all required. The dependent roadblocks to renewable and sustainable energy technologies are defined as lack of coordination among authorities, lack of information, and competition with non-renewable technologies. Moreover, linkage roadblocks have high dependence and driving powers which are insufficient infrastructure, limited awareness and consumer interest, and lack of standardized technology. Lastly, high initial investment costs, lack of subsidies and financial support programs, absence of coherent related policies, and lack of skilled and trained personnel are the driving roadblocks with high driving power however not dependent.

Progress, Challenges and Opportunities of NMR and XL-MS for Cellular Structural Biology.

The validity of protein structures and interactions, whether determined under ideal laboratory conditions or predicted by AI tools such as Alphafold2, to precisely reflect those found in living cells remains to be examined. Moreover, understanding the changes in protein structures and interactions in response to stimuli within living cells, under both normal and disease conditions, is key to grasping proteins' functionality and cellular processes. Nevertheless, achieving high-resolution identification of these protein structures and interactions within living cells presents a technical challenge. In this Perspective, we summarize the recent advancements in in-cell nuclear magnetic resonance (NMR) and in vivo cross-linking mass spectrometry (XL-MS) for studying protein structures and interactions within a cellular context. Additionally, we discuss the challenges, opportunities, and potential benefits of integrating in-cell NMR and in vivo XL-MS in future research to offer an exhaustive approach to studying proteins in their natural habitat.

How urbanization is shifting the context of nature experiences from economic to recreational

Abstract With increasing global urbanization, the proportion of the world's population engaged in the primary sector of the economy continues to decrease, leading to significant changes in the experience of nature (EoN). As a result, not only are opportunities for EoN reduced, but they are shifting structurally because the proportion of nature experiences that take place in leisure time increases relative to that which takes place in a work and production context. In order to understand the implications of this structural change, a new typology is introduced that defines experiences of nature by considering their social context: economic and recreational EoN. Economic EoN is predominantly purpose‐oriented, while recreational EoN is primarily experience‐driven. Compared to economic EoN, recreational EoN often requires less skill and knowledge while relying on stereotypical constructs of nature, demonstrated, for example, by traditional land uses and tourism, respectively. As urbanization continues, the proportion of recreational nature experiences will continue to increase, raising an important question: How can the experience‐driven, recreational relation to nature contribute to long‐term engagement and responsible stewardship? Long‐term engagement is evident in leisurely behaviour where people pursue hobbies. In urban societies, many people invest a considerable amount of time and material resources in their hobbies, while developing specific skill sets and acquiring extensive knowledge in the process. Furthermore, nature‐related hobbies enable the transformation of irrelevant economic EoN into meaningful recreational EoN, allowing the emergence of an individual perspective on and a lasting relationship with nature, as well as creating a skill‐based sense of place. Policy implications: As traditional economic EoN diminish and becomes irrelevant during the urbanization process, hobbies can help preserve ecological knowledge and skills with recreational EoN. Protected areas and other organizations curating nature experiences should create and promote experiences that relate to nature‐based hobbies and focus on supporting skill development. Read the free Plain Language Summary for this article on the Journal blog.

Planning progress: Incorporating innovation and structural change into models of economic planning

This paper addresses the challenge of incorporating innovation and structural change in models of economic planning. Previous approaches to economic planning have mostly considered the static problem of the allocation of goods and services, leaving a secondary role (if at all) for the dynamic problem of innovation and change. However, Morozov (2021) argues that the key challenge for any alternative economic system, including planning, is to incorporate a model for progress that can rival the perceived innovative and dynamic nature of capitalism. Finding previous approaches to change in planned economies to be insufficient as central elements of planning technological progress, this paper introduces two new and complementary approaches to planning innovation: Democratic accelerated missions and screening and scaling technologies. Democratic accelerated missions act on the demand side of innovation, translating democratically formulated needs for new capabilities into research and development projects to fulfill these needs. Screening and scaling technologies act on the supply side, selecting promising new technologies based on democratically decided priorities and developing them towards finished products. Both approaches draw extensively on quantitative and qualitative evidence from different strands of literature on innovation to build an empirically grounded model, with a particular focus on (1) democratic decision-making in planning innovation, and (2) incorporating insights from technology prediction and the economics of innovation to steer technological progress. The proposed model demonstrates the feasibility of planning and directing technological progress, and is a first step towards designing institutional and algorithmic structures to this end.