Metal Chains Research Articles

Four novel coordination polymers with beautiful three-dimensional frameworks as potential Fe3+/Cr2O72− sensors

Protecting water resources is the innate obligation of human beings, and detecting pollutants in water is an important work to protect water resources. In this work, we have prepared four novel coordination polymers, named {[Zn3(L)2(H2O)4]‧5H2O}n (1), {[Zn6(L)4(4,4′-bpy)(H2O)6]‧3H2O}n (2), [Cd(HL)(H2O)]n (3) and [Cd3(L)2(pyz)(H2O)3]n (4) (H3L = 1-(3-carboxybenzyl)-1H-pyrazole-3,5-dicarboxylic acid, 4,4′-bpy = 4,4′-bipyridine and pyz = pyrazine). The organic ligands exhibit various coordination patterns, making the beautiful structures of the four compounds quite different. Compounds 1, 2, and 4 all show three core clusters and form the final three-dimensional frameworks by interconnecting metal clusters and organic ligands. Meanwhile, compound 3 displays the infinite metal chain and forms the final three-dimensional framework. These four compounds were also used to detect cations/anions in the water, showing that they can selectively detect Fe3+ and Cr2O72−. The excellent anti-interference ability, limit of detection, and reproducibility suggest that these four compounds are all potential sensing materials for Fe3+ and Cr2O72−.

Rotherkopfite, KNa2(Fe2+2.5Ti4+1.5)Fe2+(Si4O12)2, a new neptunite-group mineral without essential lithium, from Rother Kopf, Eifel volcanic fields, Germany

Abstract. Rotherkopfite, KNa2(Fe2.52+Ti1.54+)Fe2+(Si4O12)2, is a new member of the neptunite group, from Rother Kopf, Roth, near Gerolstein, Eifel volcanic fields, Rhineland-Palatinate, Germany. It is found in cavities in a quartz–sanidine xenolith embedded in a vesicular alkaline basalt and is associated with fluorophlogopite and an amphibole supergroup mineral that is zoned from potassic-magnesio-fluoro-arfvedsonite on the exterior to potassic-fluoro-richterite in the core. It is presumed to have formed as the result of contact metasomatism of the xenolith by the alkaline basalt melt. Rotherkopfite occurs as brownish-red equant or tabular crystals, up to about 0.2 mm in maximum dimension. The mineral has a light-orange streak, a vitreous lustre, a Mohs hardness of ∼4.5, a brittle tenacity, a curved fracture and a density of 3.20(2) g cm−3. Optically, rotherkopfite crystals are biaxial (+), with α=1.668(5), β=1.678(5), γ=1.720(5) (white light) and 2V(meas) = 53.2(6)°. The empirical formula from electron microprobe analyses, secondary ion mass spectrometry and structure refinement is (K0.87Na0.20)Σ1.07(Na1.99Ca0.01)Σ2.00M1+M2(Fe1.662+Ti1.48Mg0.79Mn0.02)Σ3.95M3(Fe0.642+Li0.16Ti0.15Al0.01)Σ0.96(Si8.00O24). Rotherkopfite is monoclinic with space group C2/c and unit-cell parameters a=16.4599(17), b=12.5457(6), c=10.0487(7) Å, β=115.669(7)°, V=1870.3(3) Å3 and Z=4. The crystal structure (R1=0.0268 for 1324 reflections with I>2σI) is based on two interwoven three-dimensional frameworks: (1) a silicate framework made up of pyroxene-like chains of corner-sharing SiO4 tetrahedra and (2) an octahedral framework made up of chains of edge-sharing metal–oxygen octahedra. The two interwoven frameworks are bound to one another by corner sharing. K and Na are hosted in channels in the combined framework.

Implications of Lairage and Environmental Enrichment on Behavioral Responses and Skin Lesions in Finishing Pigs in a Slaughterhouse.

Different resources, such as environmental enrichment, are being evaluated in order to minimize animal stress and promote better conditions during the life cycle of animals, as consumers are increasingly concerned about animal welfare issues. Lairage represents an important stage in the swine production chain and is directly related to animal welfare. The aim of this study was to evaluate the effect of lairage time in the slaughterhouse and environmental enrichment on the level of skin lesions and behavioral responses in pigs. A total of 648 finishing pigs of both sexes were assessed before and after lairage at the slaughterhouse with a five-point scale (0 = none, to 4 = ≥16 superficial lesions or >10 deep lesions). After lairage (after slaughter), lesions were also classified according to their source (mounting, fighting, and handling). Pigs were distributed into two treatments groups during lairage: with environmental enrichment (EE) on the pen, with hanging metal chains, and with no enrichment (NE). Behavior was monitored during the first four hours of lairage. Proportional odds, mixed linear model for longitudinal data, and non-parametric Wilcoxon signed rank tests were used to analyze the relation between treatments, skin lesions, and behavior. The simple metal chains did not affect skin lesion score or pigs' behavior (p > 0.05), whereas lairage duration influenced standing (SA), sitting (S), lying (L), idleness (I), and drinking water (D) (p < 0.001). The main source of skin lesions was handling, which did not differ between treatments (EE and NE) (p > 0.05). It was observed that the severity of the lesions (highest scores of 3, 4, and 5) increased in the different anatomical regions of the pigs when compared before and after slaughter, with the exception of the frontal area, which was the same (p = 0.7547). Lairage time has a proportional relation with skin lesions, and hanging chains at the slaughterhouse pens was not enough to reduce the number of lesions and to change pig behavior.

A Three-Dimensionally Extended Metal-Organic Ladder Compound Exhibiting Proton Conduction.

Ladder systems situated in the dimensional crossover region have attracted much attention because their electronic states and physical properties depend strongly on the electronic correlations among the constituent legs. Generally, two-/three-legged transition metal-oxide ladder compounds are studied as representative ladder systems, but two-/three-dimensional (2D/3D) extensions based on such ladder systems with a few numbers of legs are difficult because of the extreme synthesis conditions. Here, for the first time, we report the successful creation of a 3D extended two-legged ladder compound, [Pt(en)(dpye)I]2(NO3)4 ⋅ 2H2O (en=ethylenediamine; dpye=1,2-Di(4-pyridyl)ethane), which is obtained by simple oxidative polymerization of a small Pt macrocyclic complex using elemental I2. The unique 3D extended lattice consists of 1D mixed-valence halogen-bridged metal chains (⋅⋅⋅Pt-I-Pt-I⋅⋅⋅) and helically arranged macrocyclic units as the constituent legs and rungs, as confirmed by single-crystal X-ray diffraction. Diffuse X-ray scattering analyses and optical measurements revealed that the out-of-phase mixed-valence Pt2+/Pt4+ arrangement arises from the weak interchain correlation among adjacent legs. In addition, this compound shows an increase in proton conductivity by a factor of up to 1000, depending on humidity.

A Three‐Dimensionally Extended Metal–Organic Ladder Compound Exhibiting Proton Conduction

AbstractLadder systems situated in the dimensional crossover region have attracted much attention because their electronic states and physical properties depend strongly on the electronic correlations among the constituent legs. Generally, two‐/three‐legged transition metal‐oxide ladder compounds are studied as representative ladder systems, but two‐/three‐dimensional (2D/3D) extensions based on such ladder systems with a few numbers of legs are difficult because of the extreme synthesis conditions. Here, for the first time, we report the successful creation of a 3D extended two‐legged ladder compound, [Pt(en)(dpye)I]2(NO3)4 ⋅ 2H2O (en=ethylenediamine; dpye=1,2‐Di(4‐pyridyl)ethane), which is obtained by simple oxidative polymerization of a small Pt macrocyclic complex using elemental I2. The unique 3D extended lattice consists of 1D mixed‐valence halogen‐bridged metal chains (⋅⋅⋅Pt−I−Pt−I⋅⋅⋅) and helically arranged macrocyclic units as the constituent legs and rungs, as confirmed by single‐crystal X‐ray diffraction. Diffuse X‐ray scattering analyses and optical measurements revealed that the out‐of‐phase mixed‐valence Pt2+/Pt4+ arrangement arises from the weak interchain correlation among adjacent legs. In addition, this compound shows an increase in proton conductivity by a factor of up to 1000, depending on humidity.

Quantum transport on the surfaces of topological nodal-line semimetals

Topological nodal-line semimetals are always characterized by the drumhead surface states at the open boundaries. In this paper we first derive an analytical expression for the surface Green’s function of a nodal-line semimetal. By making use of this result, we explore the charge and spin transport properties of a metallic chain on the surface of a nodal-line semimetal, as functions of the gate voltage applied on the top of the material. According to the size of the nodal loop, due to the coupling to the surface modes, the charge conductance in the chain is found to show a robust plateau at e2/h , or to exhibit multiple valleys at e2/h . Correspondingly, the spin polarization of the transmitted current is 100% at the plateau region, or exhibits multiple peaks at nearly 100% . This feature can be viewed as a transport signature of the topological nodal-line semimetals.

Lanthanide Metal-Organic Frameworks Exhibiting Fluoro-Bridged Extended Chains: Synthesis, Crystal Structures, and Magnetic Properties.

Two fluoro-bridged lanthanide-containing metal-organic frameworks (MOFs) were synthesized using 2,2'-bipyridine-4,4'-dicarboxylic acid (BPDC), a fluorinated modulator, and a lanthanide nitrate. The syntheses of MOFs containing Gd3+ or Tb3+ and a closely related MOF structure containing Ho3+, Gd3+, or Tb3+ are presented. The presence of the fluorinated metal chains in these MOFs is shown through single crystal X-ray diffraction, energy dispersion X-ray spectroscopy, 19F nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Magnetic measurements reveal weak antiferromagnetic exchange between the Ln3+ ions mediated by fluoride anions along the zigzag ladder chains present in the crystal structures of these MOFs.

Еще одна тайна большого цепного моста, или Qui est le Capitaine Вrun?

Purpose: To uncover new data related to the history of the Institute of Railway Engineers during the 1820s–1830s, exploring the biographical aspect of the history of the model workshop at the Institute of Railway Engineers through the little-known facts of the biography of Egor (Georgy) Frantsevich Brun, who was in charge of the workshop of the institute since 1829. Methods: The collection and analysis of historical data using published publications, reference literature, archival sources and the museum fund. Results: The precise date of the arrival of the model of the Egyptian chain bridge at the Institute of Railway Engineers has been established. The authorship of one of the oldest models in the exposition of the Central Museum of Railway Transport of the Russian Federation has been identified, which vividly demonstrates the construction of the first metal chain bridges and reflects the beginning of the development of new directions in bridge construction in Russia in the 19th century. The biography of the engineer E.F. Brun during the 1820s–1830s has been reconstructed. Practical significance: The materials are published for the first time and can be useful both for further research by specialists in the history of the first transport university of Russia, and for a wide range of interested readers.

Coins have both sides: Revealing the structure and pattern of global interdependence network for five critical metals

Evaluating the trade interdependence among countries is the key to understanding critical metal minerals security. By constructing a novel interdependence network, this paper reveals a more comprehensive world hierarchy and risk system of critical metals, and focuses on the interdependencies between China and the US-led MSP countries before and after the Sino-US trade disputes. The results indicate that the global interdependence network of critical metals has declined, with antimony interdependence being the loosest. China and the U.S. are gradually separating into different communities and driving the camp-based world pattern. In addition, the world is increasingly less dependent on China, but China is increasingly dependent on the world. China only remains the world's most indispensable in both lithium and tungsten alone, but it is the most world-dependent country in all four critical metal interdependence networks except tungsten. Meanwhile, China and Western countries such as the U.S. are at high risk of dependence on critical metal chains, while most of the others are gradually getting better. Interestingly, MSP countries and China maintain strong interdependencies. MSP countries' dependencies on China have significantly decreased, While China's dependence on MSP has gradually deepened.

111 A Suspended Molasses Block Improves Post-Mixing Welfare of Gestating Sows

Abstract Most swine production systems in the US do not include access to environmental enrichment: an improvement in the biological functioning of captive animals resulting from modifications to their environment. Optimal enrichments such as straw, hay and silage are not acceptable due to manure system and biosecurity concerns. There remains a need to develop enrichment for pigs that is biologically relevant, safe for existing systems, biosecure, sustainable and cost effective. The aim of this study was to compare the behavior and welfare of sows over 2 weeks post-mixing when given access to a suspended molasses block (B - Barastoc Swine Block) or a metal chain (C). Three replicates of 36 LW × Yorkshire sows, balanced by parity, were mixed at d 42 post service in groups of 4, 6 or 8, with one of each group size per treatment. Groups were formed with equal numbers of sows from 2 large group pens, i.e., a group of 4 was formed using 2 sows from one pen, mixed with 2 sows from a second pen, and so on. Sow behavior and animal-based welfare measures were recorded 3 days before mixing, and d 1, 6 and 13 post-mixing. Welfare measures included tear stains, lesion scores, bursitis, shoulder sores, respiratory and cleanliness scores. Behavior included passive and active human-approach tests, where the human stood for 3 min against one wall of the pen to allow sows to approach, noting number to approach and touch the human and the latency to touch. Then at the end of the test, the human actively approached each sow in turn and touched the head of the sow, noting the response of the sow on a numerical scale. Data were analyzed using 2-way ANOVA with treatment and group size as factors. There were no treatment differences in bursitis, shoulder sores and respiratory scores, and no differences in time to approach and touch the human. However, B sows had smaller tear stains (d 6 and d 13, P &amp;lt; 0.001), decreased body lesion scores (d 1 and d 6, P &amp;lt; 0.05), and better body cleanliness scores (d 1, P &amp;lt; 0.05). Human approach test measures showed habituation over time, but B sows responded less to a human approaching and touching their head than C sows (d 6, P &amp;lt; 0.05). Groups of 6 had lowest tear stain scores (d 1, d 6 and d 13, P &amp;lt; 0.05) and were cleanest (d 13, P &amp;lt; 0.05). There was also a Group size*treatment interaction with groups of 6 having the lowest lesion scores in the C treatment, but the highest in the B treatment (d 1, d 6, and d 13, P &amp;lt; 0.05). The skin lesions scores indicate that aggression was lower in the pens with the blocks. Overall, the blocks improved sow welfare over the immediate 2-week post-mixing period, though group size may impact this.

Fatigue life estimate of metallic chain links of mooring systems assuming out of plane bending: From constant amplitude to random loading

In this work, a numerical and analytical study of the fatigue life of chains in the mooring system of FPSO platforms is carried out. Initially, analytical equations are proposed to calculate the stress at the hotspot of the critical chain link, considering axial stresses generated by axial loads and out-of-plane bending (OPB). The analytical equations consider the operating angle of the mooring systems as well as the interlink angle of the links. Thus, the validation of the equations is done by comparing the stress values obtained through numerical simulations of the mooring-fairlead system, where a satisfactory correlation was observed. In addition, loads with constant and variable amplitude are generated as well as random load histories, always between the maximum and minimum operating load of the system, which represent 1/3 and 1/6 of the minimum breaking load (MBL) of the chain link. Based on the Smith-Watson-Topper (SWT) approach, the fatigue life of the chain was estimated, considering the analytical value of the stress at the hotspot based only on the axial contribution and later, due to the axial and OPB contributions. Finally, it was verified that the analytical equations were able to determine the stress values at the hotspot and that the effect of normal stress at the hotspot due to OPB can cause a severe loss in the fatigue life of the mechanical component.

MBD + C: How to Incorporate Metallic Character into Atom-Based Dispersion Energy Schemes.

The dispersion component of the van der Waals interaction in low-dimensional metals is known to exhibit anomalous "Type-C non-additivity" [Int. J. Quantum Chem. 2014, 114, 1157]. This causes dispersion energy behavior at asymptotically large separations that is missed by popular atom-based schemes for dispersion energy calculations. For example, the dispersion interaction energy between parallel metallic nanotubes at separation D falls off asymptotically as approximately D-2, whereas current atom-based schemes predict D-5 asymptotically. To date, it has not been clear whether current atom-based theories also give the dispersion interaction inaccurately at smaller separations for low-dimensional metals. Here, we introduce a new theory that we term "MBD + C". It permits inclusion of Type C effects efficiently within atom-based dispersion energy schemes such as many body dispersion (MBD) and universal MBD (uMBD). This allows us to investigate asymptotic, intermediate, and near-contact regimes with equal accuracy. (The large contact energy of intimate metallic bonding is not primarily governed by dispersion energy and is described well by the semi-local density functional theory.) Here, we apply a simplified version, "nn-MBD + C", of our new theory to calculate the dispersion interaction for three low-dimensional metallic systems: parallel metallic chains of gold atoms, parallel Li-doped graphene sheets, and parallel (4,4) armchair carbon nanotubes. In addition to giving the correct asymptotic behavior, the new theory seamlessly gives the dispersion energy down to near-contact geometry, where it is similar to MBD but can give up to 15% more dispersion energy than current MBD schemes, in the systems studied so far. This percentage increases with separation until nn-MBD + C dominates MBD at asymptotic separations.

Endoscopic removal of ingested foreign body in children: experience of a tertiary care hospital of Bangladesh

Purpose: Foreign body ingestion is a common incident in children &amp; majority of ingested foreign body removed spontaneously, few percentages (10%) remain in GI tract. The timing of endoscopy depends on some clinical &amp; radiological parameters. The aim of this study to is to observe clinical profile of foreign body ingestion in children in Bangladesh. Methods: This cross-sectional descriptive study was conducted from February 2016 to December 2019 in the department of Paediatric Gastroenterology and Nutrition, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka. A total of 29 cases of upper GI tract foreign bodies were studied. Patients with history of ingested foreign body, were clinically examined. Asymptomatic foreign body ingestion was frequently observed. Routine neck and chest X-ray in both AP and lateral views were obtained for these cases. Flexible endoscopy for foreign body extraction with suitable foreign body retriever was used to remove the foreign bodies. Data were expressed as percentage &amp; number. Results: Foreign body was commonly seen 22 (75.9%) in 1-5 years of age. Sex distribution of foreign body ingestion cases, where 15 (51.7%) were male child. Among the ingested foreign bodies only 3 (10.3%) were removed within 24 hours of ingestion, 10 (34.5%) cases were removed between 24-48 hours and the remaining 16 (55.2%) were removed after 48 hours. Coin was the most common foreign body 19(65.5%). Other foreign bodies were metallic chain 3 (10.3%), button battery 2 (6.9%), others 5 (17.2%). Conclusion: The study showed that foreign body ingestion is more common in 1-5 years age group, coin was the most commonly ingested foreign body.

Assessing the sustainability of laser powder bed fusion and traditional manufacturing processes using a parametric environmental impact model

Existing work on the relative environmental impacts of laser powder bed fusion (L-PBF) and traditional processes lacks generalizability as part design and machine settings change. We use literature reviews and power measurements to derive parametric environmental impact models with uncertainty for metal and polymer L-PBF process chains and traditional alternatives. Lead-time and cost models are derived as additional process selection metrics. The mechanistic models are functions of the part specification, batch size, and process settings.The results show the sensitivity of impacts to changes in part design/complexity and process settings is different for metal versus polymer L-PBF due to the process physics. Cradle-to-gate breakeven batch sizes (above which traditional manufacturing has lower impacts) are higher for lead-time and cost than environmental impacts, suggesting companies might increase impacts while saving time/costs. Life cycle accounting shows L-PBF enabled lightweighting, even with process improvement, falls short of environmental competitiveness for mass-producing automotive parts.

Mixed-Valence Tetrametallic Iridium Chains.

Neutral [X-{Ir2 }-{Ir2 }-X] (X=Cl, Br, SCN, I) and dicationic [L-{Ir2 }-{Ir2 }-L]2+ (L=MeCN, Me2 CO) tetrametallic iridium chains made by connecting two dinuclear {Ir2 } units ({Ir2 }=[Ir2 (μ-OPy)2 (CO)4 ], OPy=2-pyridonate) by an iridium-iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain. While the axial ligands do not significantly affect the metal-metal bond lengths, the metallic chain has a significant impact on the iridium-L/X bond distances. The complexes show free rotation around the unsupported iridium-iridium bond in solution, with a low-energy transition state for the chloride chain. The absorption spectra of these complexes show characteristic bands at 438-504 nm, which can be fine-tuned by varying the terminal capping ligands.

Failure analysis of a pair of failed chain links

The failure of a pair of metal chains during a towing operation in a particularly aggressive environment is examined. Evaluation of the cause of failure is carried out through visual observation, optical and scanning electron microscope analyses of various surfaces, including fracture surfaces, in combination with hardness and tensile tests. Visual examination revealed a high reduction in the resistant section near the contact zones between contiguous links, where the chains then failed. The chemical composition and percentage of elements present on the surface showed a high presence of corrosion products. The main cause of the chain link failure was due to corrosive wear, which markedly wore down the chain by reducing its resistant section resulting in overloading of the remaining net section area of the chain. Corrosive wear also removed the case-hardened layer induced by carbo-cementation. In order to assess the effect of corrosive wear power, an analytical evaluation was proposed. This method, although approximate, succeeds in assessing the reduction in chain strength induced by corrosive wear. Better inspection and maintenance would have allowed for early detection of the presence of the corrosive wear phenomenon, while a metal material with greater resistance to corrosion would certainly have postponed and/or prevented the manifestation of this problem, ensuring a longer service life. In this way, the initially planned safety coefficient of 2, in relation to the static breaking load, can also be reduced.

Super strong and tough anisotropic hydrogels through synergy of directional freeze-casting, metal complexation and salting out

Strong and tough ionic conductive hydrogel is one of the key raw materials for the development of high-performance flexible electronic products. However, it is still challenging to prepare ionic conductive hydrogel materials with the integration of ultra-high mechanical strength, extremely high toughness and ionic conductivity. In this work, a simple strategy is proposed to prepare super strong and tough hydrogels through multi-length scale synergistic strengthening. The directional freeze-casting would endow hydrogels with good anisotropic structure at the micro-scale and the post-treatment of soaking in the saturated Na3Cit and Al2(SO4)3 composite solution would introduce metal complexation and chain entanglement to realize network structure densification at the sub-micro and nano-scale. These effects have been proven to be positive and synergistic, which can significantly increase the tensile strength, toughness and Young's modulus of the poly(vinyl alcohol)/carboxymethyl chitosan (PVA/CMCS) hydrogel. The optimum tensile strength, toughness, Young's modulus and tear energy of PVA/CMCS/Na3Cit/Al2(SO4)3 hydrogel reach 25.9 MPa, 90.9 MJ/m3, 422.6 MPa and 118.2 MJ/m2. This super strong and tough conductive hydrogel was assembled into a sensor and combined with Morse code to realize information transmission, encryption and decryption. This work provides a new scheme for the preparation of ultra-strong ionic conductive hydrogel for flexible electronics.

Quench dynamics of the Kondo effect: Transport across an impurity coupled to interacting wires

We study the real-time dynamics of the Kondo effect after a quantum quench in which a magnetic impurity is coupled to two metallic Hubbard chains. Using an effective field theory approach, we find that for noninteracting electrons the charge current across the impurity is given by a scaling function that involves the Kondo time. In the interacting case, we show that the Kondo time decreases with the strength of the repulsive interaction and the time dependence of the current reveals signatures of the Kondo effect in a Luttinger liquid. In addition, we verify that the relaxation of the impurity magnetization does not exhibit universal scaling behavior in the perturbative regime below the Kondo time. Our results highlight the role of nonequilibrium dynamics as a valuable tool in the study of quantum impurities in interacting systems.

Aiming for dynamic behaviours of molecular metal chains.

The dynamical functions of molecular metal chains, that could be derived from unique physical and chemical properties coupled with self-assembly of metal chain components, have largely been unexplored, and this review paper focuses on the dynamic behaviours of Pd chains supported by linear tetraphosphines, meso- and rac-Ph2PCH2P(Ph)CH2P(Ph)CH2PPh2 recently reported, and the current development on fine-tuning of metal chains by introducing heterometal atoms, i.e. heterometallic molecular metal chains, that are considered as promising dynamical components in the next generation.

Electronic and topological properties of extended two-dimensional Su-Schrieffer-Heeger models and realization of flat edge bands

One-dimensional Su-Schrieffer-Heeger (SSH) chains are one of the simplest topological models and have been studied extensively. The two-dimensional $(2\mathrm{D})$ version has been confirmed to have a nontrivial topology. In this work, we further extend the $2\mathrm{D}$ SSH model by constructing different configurations, including all possible configurations with 4-site unit cells and another two complicated, but typical, configurations with 8- and 36-site unit cells, respectively. We calculate and analyze the electronic structures and topologies of these SSH models in detail and identify several rich and novel properties, such as topologically protected edge states, metallic chains with different shapes, and a bulk--edge separation in a metal system. In particular, a flat-band feature of topological edge states is obtained. By analyzing the spatial distribution of these edge states, we explain the origin of the flat edge bands and show that bonding squares play a crucial role in the formation of flat bands. Our study can be generalized to more configurations and higher dimensions, providing a basis for further theoretical and experimental explorations.