Newcastle viral disease causation web correlations with laying hen productivity.

Environmental conditions profoundly impact the health, welfare, and productivity of laying hens in commercial poultry farming. We investigated the association between microclimate variations, production indices, and histopathological responses to accidental Newcastle disease virus (NDV) infection within a controlled closed-house system. The study was conducted over seven months in a laying hen facility in Cairo, Egypt. Microclimate measurements included temperature, relative humidity (RH%), air velocity (AV), and the temperature humidity index (THI) that were obtained from specific locations on the front and back sides of the facility. Productivity indices, including the egg production percentage (EPP), egg weight (EW), average daily feed intake, and feed conversion ratio, were assessed monthly. During an NDV outbreak, humoral immune responses, gross pathology, and histopathological changes were evaluated. The results demonstrated significant (p < 0.05) variations in EPP and EW between the front and back sides except in April and May. AV had a significant (p = 0.006) positive effect (Beta = 0.346) on EW on the front side. On the back side, AV had a significant (p = 0.001) positive effect (Beta = 0.474) on EW, while it negatively influenced (p = 0.027) EPP (Beta = - 0.281). However, temperature, RH%, and THI had no impact and could not serve as predictors for EPP or EW on either farm side. The humoral immune response to NDV was consistent across microclimates, highlighting the resilience of hens. Histopathological examination revealed characteristic NDV-associated lesions, with no significant differences between the microclimates. This study underscores the significance of optimizing microclimate conditions to enhance laying performance by providing tailored environmental management strategies based on seasonal variations, ensuring consistent airflow, particularly near cooling pads and exhaust fans, and reinforcing the importance of biosecurity measures under field challenges with continuous monitoring and adjustment.

The unintentional effect of unicompartmental knee arthroplasty on extraarticular deformity and of high tibial osteotomy on intraarticular deformity for the treatment of anteromedial osteoarthritis.

INTRODUCTION: Unicompartmental Knee Arthroplasty (UKA) and High Tibial Osteotomy (HTO) are two valid options in the treatment of Anteromedial Osteoarthritis (AMOA) of the knee with UKA being mainly performed in cases of Intraarticular deformity (IA) and HTO in cases of Extraarticular deformity (EA). The exact unintentional effect of UKA on EA deformity and HTO on IA deformity is still not well understood. The aim of this study was to assess this unintentional effect of UKA on EA and HTO on IA deformities respectively. MATERIALS AND METHODS: This a single-center retrospective study in which 50 patients who underwent UKA and 50 patients who underwent medial opening wedge HTO (MWOHTO) for the treatment of AMOA were included. Overall, 35 males and 15 females underwent HTO with a mean age of 44.3 ± 11.2 years while the mean age of the UKA group was 71.8 ± 7.9 years in 23 males and 27 females. The radiological effect of UKA and HTO on each of the following angles: Hip-Knee-Ankle angle (HKA), Medial Proximal Tibial Angle (MPTA), mechanical Lateral Distal Femoral Angle (mLDFA) and Joint Line Convergence Angle (JLCA) on long film radiographs both pre- and postoperatively was measured. The postoperative values were compared to the preoperative values to detect the expected and unintended effects of each technique on IA and EA deformities. RESULTS: In the HTO group, the MPTA has changed significantly as expected from 83.1 ± 4.5 preoperatively to 88.9 ± 3.9 postoperatively (p value < 0.001) correcting the existing preoperative EA varus without overcorrection. Similarly in the UKA group, the JLCA has also changed significantly as expected to correct the IA varus from 3.8 ± 1.7 preoperatively to 0.9 ± 1 postoperatively (p value < 0.001). On the other hand, the JLCA was unintentionally changed in the HTO group from 2.6 ± 2.1 preoperatively to 1.6 ± 2.4 postoperatively (p value = 0.03) partly correcting the IA varus deformity. Similarly, the MPTA showed a significant change that occurred inadvertently in the UKA group from 84.8 ± 2.1 to 86.3 ± 1.6 postoperatively (p value < 0.001). This unintentional increase in the MPTA also partly corrected the preexisting EA varus deformity. The mLDFA did not show a significant change neither in the HTO group (p value = 0.96) nor in the UKA group (p value = 0.94). CONCLUSION: In addition to intraarticular varus correction, UKA can partly correct the extraarticular varus deformity in AMOA even when resurfacing is exclusively attempted. Additionally, intraarticular deformity can be also partially managed by HTO along with the extraarticular varus correction even without performing overcorrection.

Fixation of Mallet Fractures Using a Modified Hook Plate Technique: A Prospective Case Series of 17 Patients.

Objective Various modalities have been suggested to manage mallet fractures; however, inappropriate treatment can lead to extension lag, a swan neck deformity, or arthritis of the distal interphalangeal joint (DIPJ). The current study aimed to evaluate the results (functional, radiological, and complications) of open reduction and internal fixation (ORIF) of mallet fractures using low-cost hook plates fabricated from low-profile titanium mini plates. Methods A prospective case series of 17 consecutive patients (average age of 32.3 years) with mallet fractures (six were Wehbe Type IB and 11 were Wehbe Type IIB). Eleven (64.7%) were males. The affected hand was dominant in all patients, and the affected digit was the index in 6 (35.3%), the ring in 5 (29.4%), the small in 3 (17.65%), and the middle in 3 (17.65%) patients. The same fellowship-trained hand surgeon performed all surgeries. Results The average operative time was 37.65 minutes. After an average follow-up of 10.94 months (range 6-27), the average DIPJ motion was 50° ° (range 20°-70°), the extensor lag was noted in 4 (23.5%) patients, and complications were reported in 6 (35.29%) patients. According to Crawford criteria, 6 (35.3%) patients achieved excellent results, 7 (41.2%) achieved good results, and 4 (23.5%) achieved fair results. Conclusion The modified hook plate technique for fixation of mallet fractures is a beneficial, economical, yet demanding technique that adequately provides stable fixation to allow early DIPJ motion with acceptable functional outcomes.

Sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults: an MRI study.

BACKGROUND: The aim of this magnetic resonance imaging (MRI) study was to investigate controversial sexual dimorphism of the posterior condylar offset of the femur (the offset) and the posterior slope of the tibia (the slope) in non-arthritic knees of Egyptian adults. METHODS: On 100 male and 100 female MRIs of non-arthritic knees, linear measurements of the distal part of the femur (the offset) and the angular measurements of the proximal part of the tibia (the slope) were performed and compared regarding sex and ethnicity. The intraclass correlation coefficient (ICC) was used to test the interrater agreement. RESULTS: Both offsets and the lateral offset ratio were larger in males (p < 0.001), the medial offset ratio, and the medial slope in females (p from < 0.001 to 0.007), whereas the lateral slope was sex-free (p = 0.41). Irrespective of sex, however, the medial offset with its ratio, and the medial slope were larger than their counterparts (p < 0.001). Our means of the offsets, their ratios, and the slopes mostly differed from those of other ethnicities (p from ≤ 0.001 to 0.004). ICCs > 0.8 proved MRI's precision was high. CONCLUSION: There was a sexual dimorphism of both the offset and the medial slope in non-arthritic knees of Egyptian adults. We believe future designs of knee implants should consider these differences in order to improve postoperative range of motion and patients' satisfaction after total knee arthroplasty. Level of evidence Level III Retrospective Cohort Study. Trial registration ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

Preoperative stiffness is the most important predictor of postoperative patient's satisfaction after total knee arthroplasty.

PURPOSE: To predict the most important preoperative factor affecting the patient satisfaction after total knee arthroplasty (TKA) in trial to improve patient counselling process. METHODS: We retrospectively reviewed all patients who underwent primary TKA from January 1, 2018, to January 31, 2019, with minimum one-year follow-up for the previously collected patient-reported outcome measures (PROMs) as Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score for joint replacement (KOOS, JR) preoperative, 6 months and 12 months postoperative. RESULTS: By using Oxford knee score at 12 months as dependent variable, we found a negative moderate spearman correlation between age and Oxford knee score at 12 months postoperative. Moderate negative spearman correlation was also found between Oxford knee score at 12 months postoperative and KOOS pain, stiffness and function scores at preoperative and 6 months postoperative, denoting higher satisfaction at 12 months with less perceived stiffness, pain and limited function at baseline and 6 months postoperative. A multivariate regression analysis was done using the oxford knee score at 12 months as dependent variable to detect the predictors of oxford knee score at 12 months postoperatively and showed that younger age and less perception of stiffness at baseline were significant predictors of higher Oxford knee score: higher satisfaction at 12 months postoperative. CONCLUSION: Preoperative stiffness can predict the postoperative satisfaction score more than any other factor. We also address the importance of combining more than one PROM in assessing patients as OKS and KOOS, JR.

No benefits of knee osteotomy patient's specific instrumentation in experienced surgeon hands.

PURPOSE: To compare the clinical and radiological outcomes of patient-specific instrumentation (PSI) with the conventional free hand (FH) technique in performing coronal plane corrective knee osteotomies in terms of limb alignment and functional scores. The hypothesis is that conventional FH technique in experienced hands with proper pre-operative planning is as precise as PSI. METHODS: Patients who underwent coronal plane corrective knee osteotomies with either PSI or FH technique between 2017 and 2019 by the same senior surgeon and have a minimum of 2 years follow-up period were included in this study. A total of 91 knees (84 patients) with mean age of 42.9 ± 12.5 years who had a pre- and post-operative complete weight-bearing radiographic work-up (50 of them were performed with the FH technique and 41 by means of PSI) were included for comparison. The data were retrospectively reviewed both radiologically and clinically using the Knee Injury and Osteoarthritis Outcome Score (KOOS) sub-scores. All cases in both groups were evaluated for the following measurements: hip-knee-ankle (HKA), medial proximal tibial angle (MPTA), mechanical lateral distal femoral angle (mLDFA), and joint line convergence angle (JLCA) both preoperatively and postoperatively. In addition, FH and PSI osteotomy cases were also compared for their precision in achieving the target correction that was planned preoperatively. All cases were also evaluated clinically preoperatively and at 2-year follow-up using KOOS sub-scores and the two groups were compared. RESULTS: The mean HKA precision was 1.5 ± 0.9 in FH group and 1.3 ± 0.7 in PSI (P value = n.s.), the mean MPTA precision was 1.6 ± 1.6 in FH group and 2.1 ± 1.2 in PSI (P value = n.s.), the mean m-LDFA precision was 1.9 ± 1.7 in FH group and 1.4 ± 1.3 in PSI (P value = n.s.), and the mean JLCA precision in the FH group was 1.5 ± 1.2 and 1.7 ± 1.2 in PSI (P value = n.s.). For all the radiographic parameters, there were no statistically significant differences between the target correction and the obtained correction in both groups. Moreover, PSI and FH techniques were comparable in terms of clinical outcomes and no significant difference was found between the two groups in any of the 2-year follow-up KOOS sub-scores. CONCLUSION: Conventional FH method in the hands of experienced surgeons is as precise as PSI in reliably achieving the planned correction in different coronal plane knee corrective osteotomies. Moreover, there was also no difference between both methods in the 2-year clinical outcome scores.

In slope-changing osteotomy one millimeter is not one degree: results of an artificial intelligence-automated software analysis.

BACKGROUND: Anterior closing wedge osteotomies (ACWO) are performed in revision anterior cruciate ligament (ACL) surgery to correct an excessive posterior tibial slope (PTS). PURPOSE: With the help of automated planning software, this study investigates the assumption that 1mm of wedge height gives 1° of slope correction (1:1). METHODS: Fifty patients underwent ACWO, with the wedge height calculated using the 1:1 formula. Pre- and postosteotomy PTS were measured manually, and the achieved post-operative PTS was compared with the target PTS of 5.3° ± 1.9. The X-ray analysis was repeated virtually with the automated software, which also recommended a resection height. These parameters were then compared with the manually obtained parameters. RESULTS: Using a 1:1 formula, wedge heights of 8.5mm ± 2.3 was resected to achieve a PTS of 4.2° ± 0.32. This showed an overcorrection of 1.6° ± 0.8 from the target slope. This was consistent with the data from the automated software, which recommended a lower wedge height of 7.7mm ± 2.9. CONCLUSION: In trans-tubercle ACW, using a wedge height (mm) to slope correction (°) ratio of 1:1 can lead to slight over-correction. Automated software planning is useful for planning correction osteotomies in the sagittal plane.

Fixation of Mallet Fractures Using a Modified Hook Plate Technique: A Prospective Case Series of 17 Patients / Fixação de fraturas em martelo com técnica de placa de gancho modificada: Uma série de casos prospectivos de 17 pacientes

Abstract Objective Various modalities have been suggested to manage mallet fractures; however, inappropriate treatment can lead to extension lag, a swan neck deformity, or arthritis of the distal interphalangeal joint (DIPJ). The current study aimed to evaluate the results (functional, radiological, and complications) of open reduction and internal fixation (ORIF) of mallet fractures using low-cost hook plates fabricated from low-profile titanium mini plates. Methods A prospective case series of 17 consecutive patients (average age of 32.3 years) with mallet fractures (six were Wehbe Type IB and 11 were Wehbe Type MB). Eleven (64.7%) were males. The affected hand was dominant in all patients, and the affected digit was the index in 6 (35.3%), the ring in 5 (29.4%), the small in 3 (17.65%), and the middle in 3 (17.65%) patients. The same fellowship-trained hand surgeon performed all surgeries. Results The average operative time was 37.65 minutes. After an average follow-up of 10.94 months (range 6-27), the average DIPJ motion was 50º º (range 20º-70º), the extensor lag was noted in 4 (23.5%) patients, and complications were reported in 6 (35.29%) patients. According to Crawford criteria, 6 (35.3%) patients achieved excellent results, 7 (41.2%) achieved good results, and 4 (23.5%) achieved fair results. Conclusion The modified hook plate technique for fixation of mallet fractures is a beneficiai, economical, yet demanding technique that adequately provides stable fixation to allow early DIPJ motion with acceptable functional outcomes.

Resumo Objetivo Diversas modalidades têm sido sugeridas para o tratamento de fraturas em martelo; no entanto, o tratamento inadequado pode causar retardo de extensão, deformidade em pescoço de cisne ou artrite da articulação interfalangiana distal (AIFD). Este estudo teve como objetivo avaliar os desfechos (funcionais, radiológicos e complicações) da redução aberta e fixação interna (RAFI) das fraturas em martelo com placas de gancho de baixo custo fabricadas com mini placas de titânio de baixo perfil. Métodos Série de casos prospectivos de 17 pacientes consecutivos (idade média de 32,3 anos) com fraturas em martelo (seis do tipo IB e 11 do tipo IIB de Wehbe). Onze (64,7%) pacientes eram do sexo masculino. A mão acometida era a dominante em todos os pacientes, com acometimento do dedo indicador em seis (35,3%), anelar em cinco (29,4%), mínimo em três (17,65%) e médio em três (17,65%) pacientes. O mesmo cirurgião de mão experiente realizou todas as cirurgias. Resultados O tempo operatório médio foi de 37,65 minutos. Após um acompanhamento médio de 10,94 meses (intervalo de 6 a 27), observou-se movimento médio da AIFD de 50º (intervalo de 20º a 70º), retardo de extensão em quatro (23,5%) pacientes e complicações em seis (35,29%) pacientes. De acordo com os critérios de Crawford, os desfechos foram excelentes em seis (35,3%), bons em sete (41,2%) e regulares em quatro (23,5%) pacientes. Conclusão A técnica da placa de gancho modificada para fixação de fraturas em martelo é benéfica e econômica, mas exigente; permite fixação estável e adequada para permitir a movimentação precoce da AIFD com desfechos funcionais aceitáveis.

Debridement, Antibiotics, and Implant Retention for an Early Periprosthetic Infection After Unicompartmental Knee Arthroplasty: A Technical Note.

Early periprosthetic joint infection in unicompartmental knee arthroplasty (UKA) is shown to have a detrimental effect on the success of UKA surgery not only because of the sequences of the infection but also due to the other healthy lateral compartment. It is well known that Oxford meniscal bearing UKA is a very precise procedure that the use of any excessive force may have an injurious effect on the future prosthesis stability with a higher risk of bearing dislocation. This technical note aims at describing how to deal with a case of early periprosthetic joint infection in a female patient who underwent debridement, wash, implant retention and change of the mobile bearing insert including the demonstration of a difficult step during this procedure.

Anthropometric measurements of non-arthritic knees in an Egyptian population: an MRI-based study.

BACKGROUND: Knee anthropometric characteristics were evaluated for different ethnicities; however, data from North African populations are deficient. The primary aim was to investigate the Egyptian knees' anthropometric characteristics as a representative of North African populations. Secondary aims are as follows: (1) to study the anthropometric gender difference, (2) to compare results with other ethnic groups, and (3) to study the mismatch in comparison to geometric characteristics of modern TKA implant designs. METHODS: Two hundred normal knee MRI scans (100 females and 100 males, aging from 18 to 60) were obtained for analysis. Linear measurements (anteroposterior (AP), mediolateral (ML), and aspect ratio (AR)) of the planned cut surface of the distal femur (f) and the proximal tibia (t) were evaluated. RESULTS: A significant difference between both sexes was found, males had larger measurements in anteroposterior [fAP: 60.97 ± 3.1 vs 54.78 ± 3.3 (P < 0.001), tAP: 46.89 ± 3.0 vs 41.35 ± 2.9 (P < 0.001)] and mediolateral [fML: 74.89 ± 3.2 vs 67.29 ± 3.7 (P < 0.001), tML: 76.01 ± 3.0 vs 67.26 ± 3.2 (P < 0.001)], the mean femoral and tibial AP and ML measurements were different from other ethnic groups. None of the seven studied TKA systems matched the largest ML or the smallest AP dimensions of the distal femur in the current study population. CONCLUSION: A significant difference was found between males' and females' knee anthropometric characteristics. Some of the commonly used TKA implants in our area could not provide a perfect fit and coverage. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03622034 , registered on July 28, 2018.

Biallelic variants in HPDL cause pure and complicated hereditary spastic paraplegia.

Human 4-hydroxyphenylpyruvate dioxygenase-like (HPDL) is a putative iron-containing non-heme oxygenase of unknown specificity and biological significance. We report 25 families containing 34 individuals with neurological disease associated with biallelic HPDL variants. Phenotypes ranged from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spasticity and global developmental delays, sometimes complicated by episodes of neurological and respiratory decompensation. Variants included bona fide pathogenic truncating changes, although most were missense substitutions. Functionality of variants could not be determined directly as the enzymatic specificity of HPDL is unknown; however, when HPDL missense substitutions were introduced into 4-hydroxyphenylpyruvate dioxygenase (HPPD, an HPDL orthologue), they impaired the ability of HPPD to convert 4-hydroxyphenylpyruvate into homogentisate. Moreover, three additional sets of experiments provided evidence for a role of HPDL in the nervous system and further supported its link to neurological disease: (i) HPDL was expressed in the nervous system and expression increased during neural differentiation; (ii) knockdown of zebrafish hpdl led to abnormal motor behaviour, replicating aspects of the human disease; and (iii) HPDL localized to mitochondria, consistent with mitochondrial disease that is often associated with neurological manifestations. Our findings suggest that biallelic HPDL variants cause a syndrome varying from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spastic tetraplegia associated with global developmental delays.

COVID-19. An update for orthopedic surgeons.

The COVID-19 pandemic has affected our world in a short period of time, and the orthopedic surgery practice was not an exclusion. Elective care was deferred in most health care facilities and emergency care was continued with strict precautions. With rapid progression of the pandemic, the response of the medical community is also rapidly changing in all aspects of delivering care. This led to a large number of publications with reports, guidelines, measures, ways to react to the crisis, and post-pandemic predictions and speculations. In this review we aimed at summarizing all the relevant information to the orthopedic surgery community. To do this, a comprehensive search was performed with all related terms on two scientific search engines, PubMed and SCOPUS, and the results were filtered by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. The result was 72 articles that were further reduced to 33 articles after full text reading. The resultant information was organized under 5 main headings; the impact of pandemic on the orthopedic practice, COVID-19 and the trauma patient, elective and emergency surgeries during the pandemic, peri-operative management of the patient with COVID-19, Miscellaneous effects of the pandemic such as those on training programs and the evolution of telemedicine. This review represents the most up to date information published in the literature that is a must-know to every orthopedic surgeon.

Impact of the chemical nature and position of spacers on controlling the optical properties of silicon quantum dots.

The unique properties of silicon quantum dots (SQDs), including intriguing optical properties, biocompatibility, and ease of surface modification have made them excellent candidates for a variety of optoelectronic and biomedical applications. Unfortunately, the low quantum efficiency (QE), unstable photoluminescence, and poor colloidal stability of SQDs have hindered their wide applicability. Herein, we report the synthesis of four assemblies of SQDs (1.6-1.8 nm average diameter) functionalized with fluorescein dye through isothiocyanate (-NCS) and carboxylate (COO-) spacers in the benzene ring of the fluorescein to produce the dyads Am-SQD-Fl, DiAm-SQD-Fl, urea-SQD-Fl, and SQD-Fl. The photophysical measurements showed that the spacer played a key role in directing and controlling the optical properties of SQDs dyads, with the isothiocyanate spacer leading to a significant improvement in the QE of the dyad systems up to 65% and extending their photostability for at least one year. The interactions between the SQDs and fluorescein in the dyads Am-SQD-Fl, DiAm-SQD-Fl, and SQD-Fl were found to mainly proceed through photoinduced electron transfer at different rates, while energy transfer was confirmed to be the predominant process in the dyad urea-SQD-Fl. To demonstrate the suitability of the functionalized SQDs for bioimaging applications, the water-soluble dyads were examined for fluorescence imaging of human bone cancerous U2OS cells.

Energy/Electron Transfer Switch for Controlling Optical Properties of Silicon Quantum Dots.

The superior optical properties of Silicon Quantum Dots (SQDs) have made them of increasing interest for a variety of biological and opto-electronic applications. The surface functionalization of the SQDs with aromatic ligands plays a key role in controlling their optical properties due to the interaction of the ligands with the electronic wave function of SQDs. However, there is limited reports in literature describing the impact of spacer groups connecting the aromatic chromophore to SQDs on the optical properties of the SQDs. Herein, we report the synthesis of two SQDs assemblies (1.6 nm average diameter) functionalized with perylene-3,4,9,10-tetracarboxylic acid diimide (PDI) chromophore through N-propylurea and propylamine spacers. Depending on the nature of the spacer, the photophysical measurements provide clear evidence for efficient energy and/or electron transfer between the SQDs and PDI. Energy transfer was confirmed to be the operative process when propylurea spacer was used, in which the rate was estimated to be ~2 × 109 s-1. On the other hand, the propylamine spacer was found to facilitate electron transfer process within the SQDs assembly. To illustrate functionality, the water soluble SQD-N-propylurea-PDI assembly was proven to be nontoxic and efficient for fluorescent imaging of embryonic kidney HEK293 cells and human bone cancerous U2OS cells.

Tuning the Optical Properties of Silicon Quantum Dots via Surface Functionalization with Conjugated Aromatic Fluorophores.

Silicon Quantum Dots (SQDs) have recently attracted great interest due to their excellent optical properties, low cytotoxicity, and ease of surface modification. The size of SQDs and type of ligand on their surface has a great influence on their optical properties which is still poorly understood. Here we report the synthesis and spectroscopic studies of three families of unreported SQDs functionalized by covalently linking to the aromatic fluorophores, 9-vinylphenanthrene, 1-vinylpyrene, and 3-vinylperylene. The results showed that the prepared functionalized SQDs had a highly-controlled diameter by HR-TEM, ranging from 1.7-2.1 nm. The photophysical measurements of the assemblies provided clear evidence for efficient energy transfer from the fluorophore to the SQD core. FÓ§rster energy transfer is the likely mechanism in these assemblies. As a result of the photogenerated energy transfer process, the emission color of the SQD core could be efficiently tuned and its emission quantum efficiency enhanced. To demonstrate the potential application of the synthesized SQDs for bioimaging of cancer cells, the water-soluble perylene- and pyrene-capped SQDs were examined for fluorescent imaging of HeLa cells. The SQDs were shown to be of low cytotoxicity.

Ultrafast energy transfer in a Pd(II)-bridged bisporphyrin dyad.

A free base porphyrin/zinc(II)porphyrin dyad bridged by a Pd(II) unit exhibits an ultrafast S1 energy transfer (1.5 × 10(12) s(-1)) due to significant MO couplings between the acceptor and the donor and a non-nil atomic contribution of the Pd-atom in the frontier MOs, hence ensuring π-conjugation.

Unexpected drastic decrease in the excited-state electronic communication between porphyrin chromophores covalently linked by a palladium(II) bridge.

A dyad built up of a zinc(II) porphyrin and the corresponding free base, [Zn-Fb], fused to N-heterocyclic carbene (NHCs) ligands, respectively acting as singlet energy donor and acceptor, and a bridging trans-PdI2 unit, along with the corresponding [Zn-Zn] and [Fb-Fb] dimers were prepared and investigated by absorption and emission spectroscopy and density functional computations. Despite favorable structural and spectroscopic parameters, unexpectedly slow singlet energy transfer rates are measured in comparison with the predicted values by the Förster theory and those observed for other structurally related dyads. This observation is rationalized by the lack of large molecular orbital (MO) overlaps between the frontier MOs of the donor and acceptor, thus preventing a double electron exchange through the trans-PdI2 bridge, and by an electronic shielding induced by the presence of this same linker preventing the two chromophores to fully interact via their transition dipoles.

A drastic substituent effect on the emission properties of quinone diimine models and valuable insight into the excited states of emeraldine.

The (α-NR,α'-NR,N,N'-(C6H4C≡CSiMe3)4)[Q] models ([Q] = -N=C6H4=N-) exhibit upper excited state emissions Sn,Tn → S0 (n >1, R = Boc), similar to emeraldine, vs. a fluorescence S1 → S0 (R = H), driven by a large change in dihedral angles made by the NR-C6H4 and [Q] planes and intramolecular H-bonds.

Antenna effects in truxene-bridged BODIPY triarylzinc(II)porphyrin dyads: evidence for a dual Dexter-Förster mechanism.

The antenna process from an energy donor (BODIPY; 4',4'-difluoro-1',3',5',7'-tetramethyl-4'-bora-3a',4a'-diaza-s-indacene) in its singlet state to two acceptors (two zinc(II) 5,15-p-tolyl-10-phenylporphyrin) bridged by a central truxene residue (5',5'',10',10'',15',15''-hexabutyltruxene), 5, has been analysed by means of comparison of the energy transfer rates with those of a structurally similar ß-substituted BODIPY-(zinc(II) 5,10,15-p-tolyl-porphyrin), 6, where no conjugation is present between the donor and the two acceptors using the Förster resonance energy transfer (FRET) approximation. It is estimated that the energy transfer in operates mostly via a Dexter mechanism (>99%), and the remaining proceeds via a Förster mechanism (<1%). This information is useful for the design of future molecular devices aimed at harvesting light.