Osaka Institute of Technology

Transparent polycrystalline YAG with nearly the same optical characteristics as those of a single crystal were fabricated by a solid‐state reaction method using high‐purity powders (>99.99 wt% purity). The average grain size and relative density of the 1.1 at.% Nd:YAG ceramics obtained were about 50 μm and 99.98%, respectively. An oscillation experiment was performed on a cw laser by the diode laser excitation system using the fabricated ceramics. The experimental results indicated an oscillation threshold and a slope efficiency of 309 mW and 28%, respectively. These values were equivalent or superior to those of the 0.9 at.% Nd:YAG single crystal fabricated by the Czochralski method.

We report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star–black hole mergers. We infer the binary neutron star merger rate to be between 10 and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>1700</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:msup><a:mrow><a:mi>Gpc</a:mi></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>3</a:mn></a:mrow></a:msup><a:mtext> </a:mtext><a:msup><a:mrow><a:mi>yr</a:mi></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>1</a:mn></a:mrow></a:msup></a:mrow></a:math> and the neutron star–black hole merger rate to be between 7.8 and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>140</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:msup><c:mrow><c:mi>Gpc</c:mi></c:mrow><c:mrow><c:mo>−</c:mo><c:mn>3</c:mn></c:mrow></c:msup><c:mtext> </c:mtext><c:msup><c:mrow><c:mi>yr</c:mi></c:mrow><c:mrow><c:mo>−</c:mo><c:mn>1</c:mn></c:mrow></c:msup></c:mrow></c:math>, assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mn>44</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mrow><e:mi>Gpc</e:mi></e:mrow><e:mrow><e:mo>−</e:mo><e:mn>3</e:mn></e:mrow></e:msup><e:mtext> </e:mtext><e:msup><e:mrow><e:mi>yr</e:mi></e:mrow><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:mrow></e:math> at a fiducial redshift (<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>z</g:mi><g:mo>=</g:mo><g:mn>0.2</g:mn></g:math>). The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mo stretchy="false">(</i:mo><i:mn>1</i:mn><i:mo>+</i:mo><i:mi>z</i:mi><i:msup><i:mo stretchy="false">)</i:mo><i:mi>κ</i:mi></i:msup></i:math> with <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>κ</m:mi><m:mo>=</m:mo><m:mn>2.</m:mn><m:msubsup><m:mn>9</m:mn><m:mrow><m:mo>−</m:mo><m:mn>1.8</m:mn></m:mrow><m:mrow><m:mo>+</m:mo><m:mn>1.7</m:mn></m:mrow></m:msubsup></m:math> for <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>z</o:mi><o:mo>≲</o:mo><o:mn>1</o:mn></o:math>. Using both binary neutron star and neutron star–black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msubsup><q:mn>1.2</q:mn><q:mrow><q:mo>−</q:mo><q:mn>0.2</q:mn></q:mrow><q:mrow><q:mo>+</q:mo><q:mn>0.1</q:mn></q:mrow></q:msubsup></q:math> to <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:msubsup><s:mn>2.0</s:mn><s:mrow><s:mo>−</s:mo><s:mn>0.3</s:mn></s:mrow><s:mrow><s:mo>+</s:mo><s:mn>0.3</s:mn></s:mrow></s:msubsup><s:msub><s:mi>M</s:mi><s:mo stretchy="false">⊙</s:mo></s:msub></s:math>. We confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. We also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:msubsup><v:mn>8.3</v:mn><v:mrow><v:mo>−</v:mo><v:mn>0.5</v:mn></v:mrow><v:mrow><v:mo>+</v:mo><v:mn>0.3</v:mn></v:mrow></v:msubsup></v:math> and <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:msubsup><x:mn>27.9</x:mn><x:mrow><x:mo>−</x:mo><x:mn>1.8</x:mn></x:mrow><x:mrow><x:mo>+</x:mo><x:mn>1.9</x:mn></x:mrow></x:msubsup><x:msub><x:mi>M</x:mi><x:mo stretchy="false">⊙</x:mo></x:msub></x:math>. While we continue to find that the mass distribution of a binary’s more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mn>60</ab:mn><ab:msub><ab:mi>M</ab:mi><ab:mo stretchy="false">⊙</ab:mo></ab:msub></ab:math>, which would indicate the presence of a upper mass gap. Observed black hole spins are small, with half of spin magnitudes below <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:msub><db:mi>χ</db:mi><db:mi>i</db:mi></db:msub><db:mo>≈</db:mo><db:mn>0.25</db:mn></db:math>. While the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also observe evidence of misalignment of spins relative to the orbital angular momentum. Published by the American Physical Society 2023

The objectives of the DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) are to open a new window of observation for gravitational wave astronomy and to obtain insight into significant areas of science, such as verifying and characterizing inflation, determining the thermal history of the universe, characterizing dark energy, describing the formation mechanism of supermassive black holes in the center of galaxies, testing alternative theories of gravity, seeking black hole dark matter, understanding the physics of neutron stars and searching for planets around double neutron stars. DECIGO consists of four clusters of spacecraft in heliocentric orbits; each cluster employs three drag-free spacecraft, 1000 km apart from each other, whose relative displacements are measured by three pairs of differential Fabry–Perot Michelson interferometers. Two milestone missions, DECIGO pathfinder and Pre-DECIGO, will be launched to demonstrate required technologies and possibly to detect gravitational waves.

Fas ligand (FasL) is a membrane-type cytokine belonging to the TNF family, and induces apoptosis through its cell-surface receptor, Fas. To determine the cell types that express FasL, various mouse tissues and cell lines were examined by Northern hybridization using a mouse FasL cDNA as a probe. Among tissues, lymphoid organs (thymus, lymph node, spleen), lung, and small intestine express low levels of FasL mRNA, suggesting the role of FasL in the general immune system and mucosal immunity. The testis expressed FasL mRNA most abundantly; however, the size of FasL mRNA in the testis was slightly shorter than those in other tissues. Distribution of FasL mRNA in a panel of cell lines indicated that the FasL expression is rather restricted to the cells of T cell lineage. Activation of the splenocytes with the T cell activators such as PMA and ionomycin, Con A, anti-CD3, or even IL-2 alone induced the expression of the FasL. CD8+ splenocytes expressed the FasL more abundantly than did the CD4+ splenocytes upon activation by Con A and IL-2. Among CD4+ CTL cell lines, the FasL was expressed in all Th1 and Th0, and some Th2 clones.

We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star-black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO-Virgo detectors. The source of GW200105 has component masses, whereas the source of GW200115 has component masses and (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are and, respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of when assuming that GW200105 and GW200115 are representative of the NSBH population or under the assumption of a broader distribution of component masses. © 2021. The Author(s). Published by the American Astronomical Society.

Significant progress has been made with deep neural networks recently. Sharing trained models of deep neural networks has been a very important in the rapid progress of research and development of these systems. At the same time, it is necessary to protect the rights to shared trained models. To this end, we propose to use digital watermarking technology to protect intellectual property and detect intellectual property infringement in the use of trained models. First, we formulate a new problem: embedding watermarks into deep neural networks. Second, we propose a general framework for embedding a watermark in model parameters, using a parameter regularizer. Our approach does not impair the performance of networks into which a watermark is placed because the watermark is embedded while training the host network. Finally, we perform comprehensive experiments to reveal the potential of watermarking deep neural networks as the basis of this new research effort. We show that our framework can embed a watermark during the training of a deep neural network from scratch, and during fine-tuning and distilling, without impairing its performance. The embedded watermark does not disappear even after fine-tuning or parameter pruning; the watermark remains complete even after 65% of parameters are pruned.

Abstract Charred bark of Acacia mangium (bark charcoal), which is made of wood waste from pulp production, was applied as soil amendment for the cultivation of maize, cowpea and peanut to examine its effects on crop yield and soil chemical properties in South Sumatra, Indonesia. The yields of maize and peanut significantly increased after the application of bark charcoal under a fertilized condition in an infertile soil environment. In addition, increases in the root amount and colonization rate of arbuscular mycorrhizal (AM) fungi after bark charcoal application were also observed in maize. In general, the application of bark charcoal induced changes in soil chemical properties by increasing the pH value, total N and available P2O5 contents, cation exchange capacity, amounts of exchangeable cations and base saturation, and by decreasing the content of exchangeable Al3+. The amelioration of the soil chemical properties could be effective in highly weathered infertile tropical soils. The application of charcoal in agriculture is expected to lead to the formation of a carbon sink in soil and to increase crop yield because it has been suggested that charcoal is highly resistant to abiotic and biotic degradation, even in a soil environment.

The conventional proportional P controller has been often used as the position controller of the dc servo motor. When the unknown and inaccessible load torque, such as the coulomb friction, the gravity, and so on, is imposed on the dc servo motor, this control system has the steady-and/or transient-state error.

The current vector control method of PM (permanent magnet) motors is examined to expand the operating limits associated with inverter capacity. This control method is optimum in the sense of deriving maximum output torque within the voltage and current constraints. The effects of motor parameters are examined by computer simulation. The operating limits are greatly expanded by controlling the d- and q-axis components of the armature current according to the rotor speed. The operating limits are examined considering the demagnetization of the permanent magnet. If the permanent magnet has a straight demagnetization curve, like a rare-earth permanent magnet, the PM motor can be safely operated until the demagnetizing coefficient becomes 1.0. If wide speed range or constant power operation is desirable, a permanent magnetic with a high coercivity and a linear demagnetization curve must be used for the PM motor.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The recent detections of gravitational waves (GWs) reported by LIGO/Virgo collaborations have made significant impact on physics and astronomy. A global network of GW detectors will play a key role to solve the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitational wave Telescope), a new GW detector with two 3-km baseline arms arranged in the shape of an "L", located inside the Mt. Ikenoyama, Kamioka, Gifu, Japan. KAGRA's design is similar to those of the second generations such as Advanced LIGO/Virgo, but it will be operating at the cryogenic temperature with sapphire mirrors. This low temperature feature is advantageous for improving the sensitivity around 100 Hz and is considered as an important feature for the third generation GW detector concept (e.g. Einstein Telescope of Europe or Cosmic Explorer of USA). Hence, KAGRA is often called as a 2.5 generation GW detector based on laser interferometry. The installation and commissioning of KAGRA is underway and its cryogenic systems have been successfully tested in May, 2018. KAGRA's first observation run is scheduled in late 2019, aiming to join the third observation run (O3) of the advanced LIGO/Virgo network. In this work, we describe a brief history of KAGRA and highlights of main feature. We also discuss the prospects of GW observation with KAGRA in the era of O3. When operating along with the existing GW detectors, KAGRA will be helpful to locate a GW source more accurately and to determine the source parameters with higher precision, providing information for follow-up observations of a GW trigger candidate.

In this study we have examined for molecular heterogeneity of cell-matrix adhesions and the involvement of actomyosin contractility in the selective recruitment of different plaque proteins. For this purpose, we have developed a novel microscopic approach for molecular morphometry, based on automatic identification of matrix adhesions, followed by quantitative immunofluorescence and morphometric analysis. Particularly informative was fluorescence ratio imaging, comparing the local labeling intensities of different plaque molecules, including vinculin, paxillin, tensin and phosphotyrosine-containing proteins. Ratio imaging revealed considerable molecular heterogeneity between and within adhesion sites. Most striking were the differences between focal contacts, which are vinculin- and paxillin-rich and contain high levels of phosphotyrosine, and fibrillar adhesions, which are tensin-rich and contain little or no phosphotyrosine. Ratio imaging also revealed considerable variability in the molecular substructure of individual focal contacts, pointing to a non-uniform distribution of phosphotyrosine and the different plaque constituents. Studying the quantitative relationships between the various components of the submembrane plaque indicated that the levels of vinculin, paxillin and phosphotyrosine in adhesion sites are positively correlated with each other and negatively correlated with the levels of tensin. Tyrosine phosphorylation of focal contacts was highly sensitive to cellular contractility, and was diminished within 5 minutes after treatment with the kinase inhibitor H-7, an inhibitor of actomyosin contractility. This was followed by the loss of paxillin and vinculin from the focal adhesions. Tensin-rich fibrillar adhesions were relatively insensitive to H-7 treatment. These findings suggest a role for contractility in the generation of matrix adhesion diversity.

Retinoic acid (RA), a derivative of vitamin A, plays a pivotal role in vertebrate development. The level of RA may be determined by the balance between its synthesis and degradation. We have examined the role of CYP26, a P450 enzyme that may degrade RA, by generating mutant mice that lack CYP26. CYP26(-/-) mice exhibited anomalies, including caudal agenesis, similar to those induced by administration of excess RA. The concentration of endogenous RA, as revealed by marker gene activity, was markedly increased in the tailbud of the mutant animals, in which CYP26 is normally expressed. Expression of T (Brachyury) and Wnt3a in the tailbud was down-regulated in CYP26(-/-) mice, which may underlie the caudal truncation. The lack of CYP26 also resulted in homeotic transformation of vertebrae as well as in misspecification of the rostral hindbrain associated with anterior expansion of RA-positive domains. These results suggest that local degradation of RA by CYP26 is required for establishing an uneven distribution of RA along the anterio-posterior axis, which is essential for patterning the hindbrain, vertebrae, and tailbud.

Current supply chain is a linear economy model that directly or indirectly fulfills supply needs. But this model has some disadvantages, such as the relationships between the members of the supply chain or the lack of information for the consumer about the origin of the products. In this paper we propose a new model of supply chain via blockchain. This new model enables the concept of circular economy and eliminates many of the disadvantages of the current supply chain. In order to coordinate all the transactions that take place in the supply chain a multi-agent system is created for this paper.

We report results of a search for an isotropic gravitational-wave background (GWB) using data from Advanced LIGO's and Advanced Virgo's third observing run (O3) combined with upper limits from the earlier O1 and O2 runs. Unlike in previous observing runs in the advanced detector era, we include Virgo in the search for the GWB. The results of the search are consistent with uncorrelated noise, and therefore we place upper limits on the strength of the GWB. We find that the dimensionless energy density GW 5.8 10 -9 at the 95% credible level for a flat (frequency-independent) GWB, using a prior which is uniform in the log of the strength of the GWB, with 99% of the sensitivity coming from the band 20-76.6 Hz; GW f 3.4 10 -9 at 25 Hz for a power-law GWB with a spectral index of 2=3 (consistent with expectations for compact binary coalescences), in the band 20-90.6 Hz; and GW f 3.9 10 -10 at 25 Hz for a spectral index of 3, in the band 20-291.6 Hz. These upper limits improve over our previous results by a factor of 6.0 for a flat GWB, 8.8 for a spectral index of 2=3, and 13.1 for a spectral index of 3. We also search for a GWB arising from scalar and vector modes, which are predicted by alternative theories of gravity; we do not find evidence of these, and place upper limits on the strength of GWBs with these polarizations. We demonstrate that there is no evidence of correlated noise of magnetic origin by performing a Bayesian analysis that allows for the presence of both a GWB and an effective magnetic background arising from geophysical Schumann resonances. We compare our upper limits to a fiducial model for the GWB from the merger of compact binaries, updating the model to use the most recent datadriven population inference from the systems detected during O3a. Finally, we combine our results with observations of individual mergers and show that, at design sensitivity, this joint approach may yield stronger constraints on the merger rate of binary black holes at z 2 than can be achieved with individually resolved mergers alone.

Abstract The Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection of primordial gravitational waves, which could have been produced during the inflationary period right after the birth of the Universe. There are many other scientific objectives of DECIGO, including the direct measurement of the acceleration of the expansion of the Universe, and reliable and accurate predictions of the timing and locations of neutron star/black hole binary coalescences. DECIGO consists of four clusters of observatories placed in heliocentric orbit. Each cluster consists of three spacecraft, which form three Fabry–Pérot Michelson interferometers with an arm length of 1000 km. Three DECIGO clusters will be placed far from each other, and the fourth will be placed in the same position as one of the other three to obtain correlation signals for the detection of primordial gravitational waves. We plan to launch B-DECIGO, which is a scientific pathfinder for DECIGO, before DECIGO in the 2030s to demonstrate the technologies required for DECIGO, as well as to obtain fruitful scientific results to further expand multi-messenger astronomy.

Rose is the world's most important ornamental plant, with economic, cultural and symbolic value. Roses are cultivated worldwide and sold as garden roses, cut flowers and potted plants. Roses are outbred and can have various ploidy levels. Our objectives were to develop a high-quality reference genome sequence for the genus Rosa by sequencing a doubled haploid, combining long and short reads, and anchoring to a high-density genetic map, and to study the genome structure and genetic basis of major ornamental traits. We produced a doubled haploid rose line ('HapOB') from Rosa chinensis 'Old Blush' and generated a rose genome assembly anchored to seven pseudo-chromosomes (512 Mb with N50 of 3.4 Mb and 564 contigs). The length of 512 Mb represents 90.1-96.1% of the estimated haploid genome size of rose. Of the assembly, 95% is contained in only 196 contigs. The anchoring was validated using high-density diploid and tetraploid genetic maps. We delineated hallmark chromosomal features, including the pericentromeric regions, through annotation of transposable element families and positioned centromeric repeats using fluorescent in situ hybridization. The rose genome displays extensive synteny with the Fragaria vesca genome, and we delineated only two major rearrangements. Genetic diversity was analysed using resequencing data of seven diploid and one tetraploid Rosa species selected from various sections of the genus. Combining genetic and genomic approaches, we identified potential genetic regulators of key ornamental traits, including prickle density and the number of flower petals. A rose APETALA2/TOE homologue is proposed to be the major regulator of petal number in rose. This reference sequence is an important resource for studying polyploidization, meiosis and developmental processes, as we demonstrated for flower and prickle development. It will also accelerate breeding through the development of molecular markers linked to traits, the identification of the genes underlying them and the exploitation of synteny across Rosaceae.

Abstract The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org . The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages.

▪ Abstract Yttrium aluminum garnet (YAG) (Y 3 Al 5 O 12 ) single crystals doped with active species such as Nd and Yb have been used as laser media in solid-state lasers requiring high energy and excellent beam quality. This is because single crystals have extremely high thermal mechanical properties and optical qualities and because they enable high-efficiency laser oscillation. In 1995 the authors, using polycrystalline Nd:YAG, demonstrated a high-efficiency laser that was comparable to a single-crystal laser. Subsequently, single-longitudinal-mode oscillation, green and blue laser oscillation, and ultrashort-pulse laser oscillation were reported. Using the ceramic powder approach, the authors developed a composite laser element with a complicated structure that could not be produced by crystal growth techniques. This review discusses problems of conventional single-crystal growth, the fabrication and characteristics of ceramic lasers, laser oscillation properties (continuous-wave and pulse operation), light-scattering sources in ceramics, and typical applications of ceramic lasers.

With the current interest in cultured meat, mammalian cell-based meat has mostly been unstructured. There is thus still a high demand for artificial steak-like meat. We demonstrate in vitro construction of engineered steak-like tissue assembled of three types of bovine cell fibers (muscle, fat, and vessel). Because actual meat is an aligned assembly of the fibers connected to the tendon for the actions of contraction and relaxation, tendon-gel integrated bioprinting was developed to construct tendon-like gels. In this study, a total of 72 fibers comprising 42 muscles, 28 adipose tissues, and 2 blood capillaries were constructed by tendon-gel integrated bioprinting and manually assembled to fabricate steak-like meat with a diameter of 5 mm and a length of 10 mm inspired by a meat cut. The developed tendon-gel integrated bioprinting here could be a promising technology for the fabrication of the desired types of steak-like cultured meats.

Smart cities and artificial intelligence (AI) are among the most popular discourses in urban policy circles. Most attempts at using AI to improve efficiencies in cities have nevertheless either struggled or failed to accomplish the smart city transformation. This is mainly due to short-sighted, technologically determined and reductionist AI approaches being applied to complex urbanization problems. Besides this, as smart cities are underpinned by our ability to engage with our environments, analyze them, and make efficient, sustainable and equitable decisions, the need for a green AI approach is intensified. This perspective paper, reflecting authors’ opinions and interpretations, concentrates on the “green AI” concept as an enabler of the smart city transformation, as it offers the opportunity to move away from purely technocentric efficiency solutions towards efficient, sustainable and equitable solutions capable of realizing the desired urban futures. The aim of this perspective paper is two-fold: first, to highlight the fundamental shortfalls in mainstream AI system conceptualization and practice, and second, to advocate the need for a consolidated AI approach—i.e., green AI—to further support smart city transformation. The methodological approach includes a thorough appraisal of the current AI and smart city literatures, practices, developments, trends and applications. The paper informs authorities and planners on the importance of the adoption and deployment of AI systems that address efficiency, sustainability and equity issues in cities.