Hybrid Constructs Research Articles

Advanced hybrid composites: A comparative study of glass and basalt fiber reinforcements in erosive environments

AbstractThis study looks at how erosive wear affects hybrid composites made by vacuum infusing glass and basalt fibers into an epoxy matrix. The study uses garnet abrasives and a design experiment method to test how resistant these hybrid composites are to erosion at 30°, 60°, and 90° angles of impact. The analysis included three‐dimensional profilometry and scanning electron microscopy. Results show that glass layers enhance erosion resistance, whereas basalt layers increase wear. Key quantitative findings include erosion rates and mass loss, highlighting impingement angle and erosion time as critical factors. At a 30° angle, basalt exhibited more severe wear (erosion rate: 0.8090 mg/g for 20 s) compared to glass (erosion rate: 0.5683 mg/g). Conversely, at 90°, the erosion rate for basalt decreased to 0.3643 mg/g, indicating a decreased sensitivity to this steeper angle. According to the ANOVA, impingement angle and erosion time account for 30.08% and 50.25% of the erosion rate variance, respectively. These findings advance our understanding of material behavior in hybrid composites and emphasize the strategic selection and layering of materials for enhanced durability. This research contributes to developing more sustainable composites, demonstrating natural fibers' potential to improve mechanical properties and erosion resistance.Highlights Glass layers enhance durability against erosive forces in hybrid composites. Basalt layers accelerate erosion rates, showing a need for strategic layering. Glass fiber reinforcement significantly improves wear performance. Hybrid constructions with glass a top basalt balance flexibility and durability. Emphasizes eco‐friendly advantages of natural materials in composites.

Graphene-silymarin-loaded chitosan/gelatin/hyaluronic acid hybrid constructs for advanced full-thickness burn wound management

Burn wounds (BWs) with extensive blood loss, along with bacterial infections and poor healing, may become detrimental and pose significant rehabilitation obstacles in medical facilities. Therefore, the freeze-drying method synthesized novel hemocompatible chitosan, gelatin, and hyaluronic acid infused with graphene oxide-silymarin (CGH-SGO) hybrid constructs for application as a BW patch. Most significantly, synthesized hybrid constructs exhibited an interconnected-porous framework with precise pore sizes (≈118.52 µm) conducive to biological functions. Furthermore, the FTIR and XRD analyses document the constructs' physiochemical interactions. Similarly, enhanced swelling ratios, adequate WVTR (736 ± 78 g m−2 hr−1), and bio-degradation rates were seen during the physiological examination of constructs. Following the in vitro investigations, SMN-GO added to constructs improved their anti-bacterial (against E.coli and S. aureus), anti-oxidant, hemocompatible, and bio-compatible characteristics in conjunction with prolonged drug release. Furthermore, in vivo, implanting constructs on wounds exhibited significant acceleration in full-thickness burn wound (FT-BW) healing on the 14th day (CGH-SGO: 95 ± 2.1 %) in contrast with the control (Gauze: 71 ± 4.2 %). Additionally, contrary to gauze, the in vivo rat tail excision model administered with constructs assured immediate blood clotting. Therefore, CGH-SGO constructs with an improved porous framework, anti-bacterial activity, hemocompatibility, and biocompatibility could represent an attractive option for healing FT-BWs.

A hybrid construct of decellularized matrix and fibrin for differentiating adipose stem cells into insulin-producing cells, an optimized in vitro assessment.

The generation of insulin-producing cells (IPCs) is an attractive approach for replacing damaged β cells in diabetic patients. In the present work, we introduced a hybrid platform of decellularized amniotic membrane (dAM) and fibrin encapsulation for differentiating adipose tissue-derived stem cells (ASCs) into IPCs. ASCs were isolated from healthy donors and characterized. Human AM was decellularized, and its morphology, DNA, collagen, glycosaminoglycan (GAG) contents, and biocompatibility were evaluated. ASCs were subjected to four IPC differentiation methods, and the most efficient method was selected for the experiment. ASCs were seeded onto dAM, alone or encapsulated in fibrin gel with various thrombin concentrations, and differentiated into IPCs according to a method applying serum-free media containing 2-mercaptoethanol, nicotinamide, and exendin-4. PDX-1, GLUT-2 and insulin expression were evaluated in differentiated cells using real-time PCR. Structural integrity and collagen and GAG contents of AM were preserved after decellularization, while DNA content was minimized. Cultivating ASCs on dAM augmented their attachment, proliferation, and viability and enhanced the expression of PDX-1, GLUT-2, and insulin in differentiated cells. Encapsulating ASCs in fibrin gel containing 2 mg/ml fibrinogen and 10 units/ml thrombin increased their differentiation into IPCs. dAM and fibrin gel synergistically enhanced the differentiation of ASCs into IPCs, which could be considered an appropriate strategy for replacing damaged β cells.

Interface construction of phosphorus-based hybrid with micro/nano hierarchical structure toward intumescent flame-retardant epoxy resins with robust mechanical properties

The facile strategy for constructing phosphorus-based hybrid (APP@Zn-PT) is proposed to the simultaneous optimization of flame-retardant properties and mechanical properties of epoxy resins (EP), which is a long-term concern for the intumescent flame-retardant systems. Herein, APP@Zn-PT was fabricated via the assembly of nano-sheet phosphorus-containing triazole-zinc complex (Zn-PT) on the surface of ammonium polyphosphate micro-particles (APP). Notably, EP modified with APP@Zn-PT synchronously displayed highly fire-safe performance and excellent mechanical properties, which is seldom found in the traditionally intumescent flame-retardant EP systems. In the presence of 7 wt% APP@Zn-PT, EP acquired a high limiting oxygen index (LOI) of 31.1 %, and succeeded to meet the requirement for a UL-94 V-0 rating. Meanwhile, the results of cone calorimeter test (CCT) showed that the crucial parameters involving smoke production and heat release of EP/APP@Zn-PT presented significant decrease, that total smoke production (TSP) was dropped from 55.7 m2 of EP to 36.2 m2, and the peak of heat release rate (PHRR) was decreased from 1156 to 384 kW/m2. In addition, the interfacial interaction of APP@Zn-PT in epoxy matrix was improved as compared to APP due to the embedment of nano-sheet Zn-PT, which possessed reinforcing effect as well, and thereby the mechanical performances of EP/APP@Zn-PT were superior to neat EP and EP/APP. Generally, this work lays a foundation for the construction of phosphorus-based micro-nano hybrids, showing a great potential in high-performance polymers for practical application.

Optimized Transverse–Longitudinal Hybrid Construction for Sustainable Design of Welded Steel Plate Girders

I-section girders with different types of steel in the flanges and web (fyf > fyw, respectively) are known as transverse hybrid girders. These have proven to be more economical than their homogeneous counterparts. However, the use of hybrid configurations in the longitudinal direction of the element has yet to be studied. This paper uses optimization techniques to explore the possibility of constructing transverse and longitudinally hybrid (TLH) steel girders. The optimization objective is to minimize the manufacturing cost, including seven activities besides the material cost. The geometrically double symmetric I-girder design subjected to a uniform transverse load is performed using Eurocode 3 specifications. Nine case studies are implemented, varying the element span (L) and the applied load. The results show that establishing various configurations along the length of the element is beneficial. The optimum number of transition points is six, meaning the girder will have four configurations, i.e., one central and three others symmetrically distributed toward each half of the element. The optimum position for the first transition would be at 0.24∗(L/2), the second at 0.40∗(L/2), and the third at 0.60∗(L/2). The optimum extreme configuration is usually homogeneous (fyf = fyw = 235 MPa). The others increase the steel quality in the plates, maintaining hybrid arrangements to reach the central one that usually remains with S700 steel for the flanges and S355 for the web. The study shows that TLH configurations are more effective for elements with larger spans. By applying the formulated design recommendations in a different case study, the manufacturing cost dropped by over 50% compared to the traditionally designed element and by more than 10% relative to the optimized element with a homogeneous configuration. The study’s limitations and encouraging results suggest future lines of research in this area.

Advancing the circular economy and environmental sustainability with timber hybrid construction in South Korean public building

Timber is attracting attention as an alternative to conventional materials owing to the carbon sequestration effect during the growth process and the low carbon impact of timber use. Recently, carbon reduction, environmental impact reduction, and circular economy (CE) have been considered for sustainable development. There is a need to evaluate effective buildings in terms of CE and environmental impact, and timber has advantages in terms of circularity and environmental impact. However, few studies have quantified both environmental impact and circularity of timber buildings. In this study, environmental impact was introduced into the Building Circularity Indicators (BCI; a method of evaluating the circularity of materials and buildings). Then, the material circularity and environmental impact were verified through a timber hybrid case study of an actual public building using LCA and BCI. Environmental impact reductions of −13.5 %, −11.5 %, and −5.0 % were achieved by the hybrid alternative that applied timber to the structure, the alternative that excluded the core, and the alternative that applied it only to the exterior wall, respectively. Furthermore, the BCI improved from 0.26 for the concrete structure to 0.31, 0.29, and 0.25, for the respective timber hybrid buildings mentioned above. The research results would aid designers and policymakers in their initial planning by verifying the realistically quantified environmental impact savings and circularity. In addition, as an example of introducing environmental impact into the BCI, it would contribute to the reduction of the disparity between the circularity indicators and environmental impact.

Expression of Concern: A novel hybrid construction of MnMoO4 nanorods anchored graphene nanosheets; an efficient electrocatalyst for the picomolar detection of ecological pollutant ornidazole in water and urine samples

Expression of Concern: A novel hybrid construction of MnMoO4 nanorods anchored graphene nanosheets; an efficient electrocatalyst for the picomolar detection of ecological pollutant ornidazole in water and urine samples

Research of an autonomous power source for elec-tric vehicles and their charging infrastructure

Research of an autonomous power source for elec-tric vehicles and their charging infrastructure

Fibroblasts/three-dimensional scaffolds complexes promote wound healing in rats with skin defects

ABSTRACT We aim to construct a three-dimensional nano-skin scaffold material in vitro and study its promoting effect on wound healing in vivo. In this study, hybrid constructs of three-dimensional (3D) scaffolds were successfully fabricated by combination of type I collagen (COL-1) and polylactic-glycolic acid (PLGA). Fibroblasts and human umbilical cord mesenchymal stem cells (hUCMSCs) were used to implanted into 3D scaffolds and constructed into SD skin scaffolds in vitro. Finally, the fibroblasts/scaffolds complexes were inoculated on the surface of rat wound skin to study the promoting effect of the complex on wound healing. In our study, we successfully built a 3D scaffold, which had a certain porosity. Meanwhile, the content of COL-1 in the cell supernatant of fibroblast/scaffold complexes was increased. Furthermore, the expression of F-actin, CD105, integrin β, VEGF, and COL-1 was up-regulated in hUCMSC/scaffold complexes compared with the control group. In vivo, fibroblast/scaffold complexes promoted wound healing in rats. Our data suggested that the collagen Ⅳ and vimentin were elevated and collagen fibers were neatly arranged in the fibroblast/scaffold complex group was significantly higher than that in the scaffold group. Taken together, fibroblast/scaffold complexes were expected to be novel materials for treating skin defects.

Structural Differences at Quadruplex-Duplex Interfaces Enable Ligand-Induced Topological Transitions.

Quadruplex-duplex (QD) junctions, which represent unique structural motifs of both biological and technological significance, have been shown to constitute high-affinity binding sites for various ligands. A QD hybrid construct based on a human telomeric sequence, which harbors a duplex stem-loop in place of a short lateral loop, is structurally characterized by NMR. It folds into two major species with a (3+1) hybrid and a chair-type (2+2) antiparallel quadruplex domain coexisting in a K+ buffer solution. The antiparallel species is stabilized by an unusual capping structure involving a thymine and protonated adenine base AH+ of the lateral loop facing the hairpin duplex to form a T·AH+·G·C quartet with the interfacial G·C base pair at neutral pH. Addition and binding of Phen-DC3 to the QD hybrid mixture by its partial intercalation at corresponding QD junctions leads to a topological transition with exclusive formation of the (3+1) hybrid fold. In agreement with the available experimental data, such an unprecedented discrimination of QD junctions by a ligand can be rationalized following an induced fit mechanism.

Enhancing Adhesion of Fibrin-Based Hydrogel to Polythioether Polymer Surfaces.

The development of stable (bio)hybrid constructs composed of scaffolds and (bio)matrices is a major challenge in the field of tissue engineering. In the present work, the adhesion of fibrin-based hydrogels to the surface of polythioether-based polymers relevant to the 3D printing of polymer scaffolds produced by thiol-ene click chemistry was investigated. Adhesion properties were characterized by single-lap tensile shear testing. Both the sample preparation and the test method were optimized for the analysis of fibrin gel bonding to the polythioether surface. Our experimental results show that even without further modification, an adhesion between the fibrin hydrogel and polythioether is substantial, with an adhesion strength of 4.9 ± 1.0 kPa. To further improve the bonding, linear functional poly(N-vinylpyrrolidone-co-glycidyl methacrylate) (PVP-co-GMA) copolymers were used that are known for covalently binding to fibrin. The maximum adhesion strength in our study was found to be 18.4 ± 3.4 kPa. The pure PVP-co-GMA copolymers also demonstrate covalent binding to the thiol-ene-based polymers with a maximum adhesion strength of 32.2 ± 2.7 kPa. Therefore, compared to pure fibrin, the presence of copolymer coating both on the polythioether surface and in the fibrin gel led to a significant increase of the adhesion strength by a factor of 1.6.

Bending Behavior of Hybrid Timber-Steel Beams.

Driven by climate change and the need for a more sustainable construction sector, policy is increasingly demanding and promoting timber hybrid construction methods. In the German state of Baden-Württemberg, every new public building has to be of timber or timber hybrid construction (Holzbauoffensive BW). The objective of multi-story buildings with large floor spans can only be achieved in a resource-efficient way by hybrid constructions combining timber and steel components. A research project recently completed at the Karlsruhe Institute of Technology was aimed at the development and systematic investigation of hybrid bending beams in which an advantageous combination of the materials steel and timber is used. For this purpose, steel profiles are integrated into timber cross-sections in a shear-resistant manner by adhesive bonding. As part of the experimental, numerical and analytical investigations, different cross-sections of steel and timber, as well as different construction materials, were considered (GL24h, LVL48p, LVL80p, S355 and S420). The results of large-scale four-point bending tests illustrate the potential of this new hybrid construction method. Depending on the geometry and material combinations tested, the bending stiffness could be increased by up to 250%, and the load-carrying capacity by up to 120%, compared to a glulam beam with identical dimensions.

Evaluating the measurement of the velocity level difference for building constructions which combine Type A and Type B elements

The standard ISO 12354 outlines a method of predicting the transmission of structure-borne noise in buildings based on data measured in a laboratory or in the field, measured in part according to the standard ISO 10848. The ISO 10848 standard describes procedures for the measurement of both the normalized flanking level difference and the velocity level difference of flanking paths through different building constructions and the junctions between them. Both the normalized flanking level difference and the velocity level difference were measured for a hybrid construction of a cross-lamented timber floor (Type A element) connected to lightweight timber walls (Type B elements) in the National Research Council Canada’s four room flanking facility. The predicted normalized level differences are compared against the measured values to evaluate the prediction method for constructions that mix Type A and Type B elements.

Does the addition of convex uniplanar screws in hybrid constructs improve 3D surgical correction in thoracic adolescent idiopathic scoliosis posterior fusion?

Hybrid techniques using thoracic sublaminar bands have proved their efficacy in adolescent idiopathic scoliosis posterior fusion, but clinical axial correction sometimes remained disappointing. One solution found was "the frame technique" and the second alternative was the replacement of the convex sublaminar bands by periapical uniplanar screws. The goal of this study was to compare clinical and radiological outcomes of both techniques in a consecutive cohort of adolescent idiopathic scoliosis patients. All patients undergoing primary posterior fusion for thoracic adolescent idiopathic scoliosis between January 2017 and March 2020 were included. Two groups were compared: Group 1 with thoracic sublaminar bands only and Group 2 with periapical uniplanar screws. All patients underwent standing stereoradiographs. The main frontal, sagittal, and axial (apical vertebra rotation) radiological parameters of interest were analyzed. Functional outcomes were assessed using the Scoliosis Research Society 30 score. A total of 147 adolescents were included (Group 1, n = 73 and Group 2, n = 74 patients). In the frontal plane, a greater reduction index was observed in Group 2 (68% versus 62%, p < 0.001) as well as a better apical axial correction (67.8% versus 46.6%, p = 0.03). The number of thoracoplasty performed was reduced (6.7% versus 20.5%, p = 0.02) in Group 2, with a significant decrease in the rate of mechanical complication. No significant loss of correction was observed during follow-up in any of the group. The adjunction of convex uniplanar screws at the periapical levels improved the three-dimensional surgical correction of thoracic adolescent idiopathic scoliosis treated with hybrid constructs. level III, retrospective comparative study.

Hybrid and ensemble models by coupled with automated meta-heuristic algorithms for compressive and flexural strength and slump of high-performance concrete

High-performance concrete (HPC) is a specialized type of concrete designed to meet stringent performance and uniformity standards that are difficult to achieve with conventional materials and standard mixing, placing, and curing methods. The testing process to determine the mechanical properties of HPC specimens is complex and time-consuming, and making improvements can be difficult after the test result does not meet the required properties. Anticipating concrete characteristics is a pivotal facet in the realm of High-Performance Concrete (HPC) manufacturing. Machine learning (ML)-driven models emerge as a promising avenue to tackle this formidable task within this context. This research endeavors to employ a synergy of ML hybrid and ensemble frameworks for the prognostication of the mechanical attributes within HPC, encompassing compressive strength (CS), slump (SL), and flexural strength (FS). The formulation of these hybrid and ensemble constructs was executed through the integration of Support Vector Regression (SVR) with three distinct meta-heuristic algorithms: Prairie Dog Optimization (PDO), Pelican Optimization Algorithm (POA), and Mountain Gazelle Optimizer (MGO). Some criteria evaluators were used in the training, validation, and testing phases to assess the robustness of the established models, and the best model was proposed for practical applications through comparative analysis of the results. As a result, the hybrid and ensemble models were the potential methods to predict concrete properties accurately and efficiently, thereby reducing the need for expensive and time-consuming testing procedures. In general, the ensemble model, i.e., SVPPM, had a more suitable performance with high values of R2 equal to 0.989 (MPa), 0.984 (mm), and 0.992 (MPa) and RMSE = 3.82 (MPa), 9.5 (mm), and 0.30 (MPa) for CS, SL, FS compared to other models, respectively.

Cross-contamination of CRISPR guides and other unrelated nucleotide sequences among commercial oligonucleotides.

Custom oligonucleotides (oligos) are widely used reagents in biomedical research. Some common applications of oligos include polymerase chain reaction (PCR), sequencing, hybridization, microarray, and library construction. The reliability of oligos in such applications depends on their purity and specificity. Here, we report that commercially available oligos are frequently contaminated with nonspecific sequences (i.e. other unrelated oligonucleotides). Most of the oligos that we designed to amplify clustered regularly interspersed palindromic repeats (CRISPR) guide sequences contained nonspecific CRISPR guides. These contaminants were detected in research-grade oligos procured from eight commercial oligo-suppliers located in three different geographic regions of the world. Deep sequencing of some of the oligos revealed a variety of contaminants. Given the wide range of applications of oligos, the impact of oligo cross-contamination varies greatly depending on the field and the experimental method. Incorporating appropriate control experiments in research design can help ensure that the quality of oligo reagents meets the intended purpose. This can also minimize risk depending on the purposes for which the oligos are used.

The Evidence for the Use of Osteobiologics in Hybrid Constructs (Anterior Cervical Discectomy and Fusion and Total Disc Replacement) in Multilevel Cervical Degenerative Disc Disease: A Systematic Review.

Systematic review. Examine the clinical evidence for the use of osteobiologics in hybrid surgery (combined anterior cervical discectomy and fusion (ACDF) and total disc replacement (TDR)) in patients with multilevel cervical degenerative disc disease (DDD). PubMed and Embase were searched between January 2000 and August 2020. Clinical studies investigating 18-80 year old patients with multilevel cervical DDD who underwent hybrid surgery with or without the use of osteobiologics were considered eligible. Two reviewers independently screened and assessed the identified articles. The methodological index for non-randomized studies (MINORS) tool and the risk of bias (RoB 2.0) assessment tool were used to assess risk of bias. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was used to evaluate quality of evidence across studies per outcome. Eleven studies were included. A decrease in cervical range of motion was observed in most studies for both the hybrid surgery and the control groups consisting of stand-alone ACDF or TDR. Fusion rates of 70-100% were reported in both the hybrid surgery and control groups consisting of stand-alone ACDF. The hybrid surgery group performed better or comparable to the control group in terms of adjacent segment degeneration. Studies reported an improvement in visual analogue scale for pain and neck disability index values after surgery compared to preoperative scores for both treatment groups. The included studies had moderate methodological quality. There is insufficient evidence for assessing the use of osteobiologics in multilevel hybrid surgery and additional high quality and controlled research is deemed essential.

AO Spine Guideline for the Use of Osteobiologics (AOGO) in Anterior Cervical Discectomy and Fusion for Spinal Degenerative Cases.

Guideline. To develop an international guideline (AOGO) about the use of osteobiologics in anterior cervical discectomy and fusion (ACDF) for treating degenerative spine conditions. The guideline development process was guided by AO Spine Knowledge Forum Degenerative (KF Degen) and followed the Guideline International Network McMaster Guideline Development Checklist. The process involved 73 participants with expertise in degenerative spine diseases and surgery from 22 countries. Fifteen systematic reviews were conducted addressing respective key topics and evidence was collected. The methodologist compiled the evidence into GRADE Evidence-to-Decision frameworks. Guideline panel members judged the outcomes and other criteria and made the final recommendations through consensus. Five conditional recommendations were created. A conditional recommendation is about the use of allograft, autograft or a cage with an osteobiologic in primary ACDF surgery. Other conditional recommendations are about the use of osteobiologic for single- or multi-level ACDF, and for hybrid construct surgery. It is suggested that surgeons use other osteobiologics rather than human bone morphogenetic protein-2 (BMP-2) in common clinical situations. Surgeons are recommended to choose 1 graft over another or 1 osteobiologic over another primarily based on clinical situation, and the costs and availability of the materials. This AOGO guideline is the first to provide recommendations for the use of osteobiologics in ACDF. Despite the comprehensive searches for evidence, there were few studies completed with small sample sizes and primarily as case series with inherent risks of bias. Therefore, high-quality clinical evidence is demanded to improve the guideline.

Porphyrin-Polyoxotungstate Molecular Hybrid as a Highly Efficient, Durable, Visible-Light-Responsive Photocatalyst for Aerobic Oxidation Reactions.

Organic-polyoxometalate (POM) hybrids have recently attracted considerable interest because of their distinctive properties and wide-ranging applications. For the construction of organic-POM hybrids, porphyrins are promising building units owing to their optical properties and reactivity, including strong visible-light absorption and subsequent singlet-oxygen (1O2*) generation. However, the practical utilization of porphyrins as photocatalysts and photosensitizers is often hindered by their own degradation by 1O2*. Therefore, there is a substantial demand for the development of porphyrin-derived photocatalysts with both high efficiency and durability. Herein, we present a porphyrin-polyoxotungstate molecular hybrid featuring a face-to-face stacked porphyrin dimer (I) fastened by four lacunary polyoxotungstates. Hybrid I exhibited remarkable efficiency and durability in photocatalytic aerobic oxidation reactions, and the selective oxidation of various dienes, alkenes, sulfides, and amines proceeded using just 0.003 mol % of the catalyst. Mechanistic investigations suggested that the high activity of I stems from the efficient generation of 1O2*, resulting from the heavy-atom effect of POMs. Furthermore, despite its high efficiency in 1O2* generation compared to free porphyrins, I exhibited superior durability against 1O2*-induced degradation under photoirradiation.

Grammatical Object Passives in Yucatec Spanish

Yucatec Spanish displays a type of sentence that appears to mix elements of an active impersonal and a passive. For example, “te castigaron por mi tío” may be interpreted as “you were punished by my uncle”, where a by-phrase headed by the preposition por introduces an agent rather than a cause or reason. The verb has active morphology—it is always third-person plural, and accusative clitics (e.g., te) and DOM-marked objects are possible. This type of sentence, which I descriptively label an active–passive (A-P) hybrid, has been mentioned in previous literature on contact varieties in Mayan-speaking regions of Mexico and Guatemala, but it has not been precisely described or analyzed formally. I argue that A-P hybrid constructions are instances of grammatical object passives. Grammatical object passives have certain active properties—accusative case is assigned to a theme argument and the morphology of the verb is active, but like passives, they require that the expression of the agent be a by-phrase rather than a grammatical subject. I claim that this is possible in this variety of Spanish due to the emergence of a null pronoun, absent in other varieties of Spanish, that can merge in the specifier of Voice and restrict, rather than saturate, an agent argument, permitting the subsequent addition of a third-person by-phrase. I demonstrate that this analysis is able to explain its hybrid properties as well as other person restrictions on the by-phrases that express the agent. Finally, I describe avenues of future research that will help discern the role that language contact may have played in the emergence of A-P hybrids.