Successful Fitting Research Articles

Therapeutic Strategies in 103 Children with Congenital Microphthalmos.

Congenital microphthalmos can either occur alone (simple microphthalmos) or be associated with other ocular malformations, such as sclerocornea or cataract (complex microphthalmos). As this is a rare condition, there are no uniform recommendations for treatment. Retrospective case series of 103 patients or a total of 114 eyes with congenital microphthalmos, with reporting of age, sex, visual acuity, pupil reaction, axial length, horizontal width of the palpebral fissure, type of therapy performed and complications. All patients would have been able to be fitted with a prosthesis primarily. The size of the palpebral fissure depended on the underlying findings: "bilateral microphthalmos" < "microphthalmos and healthy fellow eye" < "microphthalmos and fellow anophthalmos". In order to assess visual (residual) function in an infant in the first weeks or months of life, the pupillary response is of the upmost importance in deciding on therapy, especially in unilateral disease, and as assessed with the indirect light response of the healthy eye. In about half of the cases, conservative prosthetic treatment was sufficient. After the successful initial fitting of a prosthesis, the prosthesis was enlarged according to the ocularist's instructions. If the eye length difference was so large that symmetry could not be achieved even with a double-walled prosthesis, volume filling with retrobulbar implanted self-swelling pellet expanders (osmed GmbH, Ilmenau) was offered. In almost one third of the patients, no surgical therapy or prosthetic treatment was performed. The reason for this was usually the presence of minimal visual function of the microphthalmos - ranging from light perception to hand movements. In the case of visual function of the microphthalmos, surgical measures should not be indicated or only with extreme caution, since the preservation of the existing visual acuity must be regarded as having priority over the cosmetic findings. In cases of asymmetry or underdeveloped palpebral fissure, therapy can be started early in the first year of life without fear of resulting complications.

Improved CenterNet for Accurate and Fast Fitting Object Detection

Accurate and fast detection of typical fittings is the prerequisite of condition monitoring and fault diagnosis. At present, most successful fitting detectors are anchor‐based, which are challenging to meet the requirements of edge deployment. In this paper, we propose a novel anchor‐free method called HRM‐CenterNet. Firstly, the lightweight MobileNetV3 is introduced into CenterNet to extract multi‐scale features of different layers. In addition, the lightweight receptive field enhancement module is proposed for the deep layer features to further enhance the characterization power of global features and generate more accurate heatmaps. Finally, the high‐resolution feature fusion network with iterative aggregation is designed to reduce the loss of spatial semantic information in subsampling and further improve the accuracy of small and occlusion objects. Experiments are carried out on the TFITS and PASCAL VOC datasets. The results show that the size of the network is more than 60% lower than that of CenterNet. Compared with other detectors, our method achieves comparable accuracy with all accurate models at a much faster speed and meets the performance requirements of real‐time detection.

Transfemoral Osseointegration-a self-case study and physiotherapy assessment.

A patient (the first author) with a preexisting right side transfemoral amputation (20 years before) had osseointegration surgery. She was assigned a physiotherapist (the second author) and began a rehabilitation program. We provide a unique insight into the first 18 months of rehabilitation after insertion of an osseointegration bone anchor from a physiotherapist and patient perspective with the intention of informing practitioners, patients, and potential patients about the experience and identifying potential areas for improvements in the rehabilitation protocol. The experience was tracked by both the patient and the physiotherapist for 18 months post-surgery. The physiotherapist followed a specific protocol with the patient in the first part of the recovery stage. The patient kept records of subjective experiences over the same period. Loading and physiotherapy were completed in line with the protocol for the first 12-week phase including successful fitting of the prosthetic limb on day 12. Physiotherapy and other interventions evolved to meet the patient's needs over the 18-month period. The patient progressed through her rehabilitation, and new data about the patient's experience were gathered. Following the protocol enabled the patient to progress through her rehabilitation. Unforeseen setbacks (abscesses and inflammation/entheseopathies) slowed this process to some extent. Findings from these data can be used to help inform and improve future rehabilitations for patients with osseointegration: patients can be advised about possible setbacks and physiotherapy, and other interventions can be developed to treat should these problems arise.

Factors associated with unsuccessful pessary fitting and reasons for discontinuation in Korean women with pelvic organ prolapse.

ObjectiveTo identify the factors associated with unsuccessful pessary fitting and reasons for pessary discontinuation in Korean women with pelvic organ prolapse (POP).MethodsThe medical records of 234 patients who underwent pessary fitting for the management of symptomatic POP were retrospectively reviewed. A ring pessary with or without support was used. Successful pessary fitting was defined as the ability to wear a pessary for 2 weeks without any discomfort. Factors associated with unsuccessful pessary fitting were determined using a multivariable logistic regression analysis. A Kaplan-Meier survival curve was obtained to examine the probability of continuing pessary use over the follow-up period. The reasons for the discontinuation of pessary were identified.ResultsTwo-hundred-and-twenty-five women were included in the analysis. The rate of unsuccessful pessary fitting was 40%. Prior hysterectomy (odds ratio [OR], 4.13; 95% confidence interval [CI], 1.81–9.42) and POP quantification stage III–IV (OR, 2.49; 95% CI, 1.28–4.85) were independent risk factors for unsuccessful pessary fitting. Among the patients with successful pessary fitting, the median time to discontinuation of pessary use was 4 years. The most common causes of discontinued use were vaginal erosion (45.3%) and urinary incontinence (26.5%).ConclusionPatients with a history of hysterectomy and advanced-stage POP are at risk for an unsuccessful fitting of the ring pessary. Vaginal erosion is the main reason for discontinued use among patients with successful pessary fitting.

Evaluation of Topical Mitomycin-C Eye Drops After Reconstructive Surgery for Anophthalmic Contracted Socket.

PurposeTo report the outcomes of using topical mitomycin-C (MMC) after reconstructive surgery for contracted socket and to compare the results with those of the conventional postoperative treatment.Patients and MethodsThe medical records of patients who underwent reconstructive surgery for contracted anophthalmic socket were retrospectively reviewed. Based on the postoperative treatment protocol, two groups of patients were identified; group I (15 patients) who received topical MMC drops (0.02%) 4 times daily for 6 weeks and group II (15 patients) who received the conventional treatment (topical antibiotic-steroid combination). Preoperative data were extracted for age, gender, cause and timing of anophthalmia, history of previous surgeries, preoperative forniceal depth and socket volume (SV). The main postoperative outcome measures were superior fornix depth (SFD), inferior fornix depth (IFD) and SV at the end of 6th postoperative month. Prosthesis fitting and complications were also considered for analysis.ResultsThe mean preoperative IFD was 1.67±0.04 mm in group I and 1.58±0.37 mm in group II, by the end of the 6th postoperative month it increased to 6.1 ±0.27 mm and 5.12 ±0.25mm, respectively. The mean preoperative SFD in group I was 8.3±0.9 mm and 8.9±1.1 mm in group II, by the end of the 6th postoperative month SFD became 13.4±1.2 mm and 10.2±1.4 mm in groups I and II, respectively. The mean SV measured six months postoperatively was 1.9±0.2 mL and 1.3±0.09 mL in groups I and II, respectively. These differences in the postoperative SFD, IFD and SV between both groups were statistically significant. More cases reported successful fitting in group I than in group II but this difference was not statistically significant.ConclusionPostoperative use of topical MMC is associated with higher forniceal depth and greater SV when compared to the conventional treatment in socket reconstructive surgeries with amniotic membrane graft (AMG).

Epicyclic oscillations in spinning particle motion around Kerr black hole applied in models fitting the quasi-periodic oscillations observed in microquasars and AGNs

The study of the quasi-periodic oscillations (QPOs) of X-ray flux observed in the stellar-mass black hole (BH) binaries or quasars can provide a powerful tool for testing the phenomena occurring in strong gravity regime. We thus fit the data of QPOs observed in the well known microquasars as well as active galactic nuclei (AGNs) in the framework of the model of geodesic oscillations of Keplerian disks modified for the epicyclic oscillations of spinning test particles orbiting Kerr BHs. We show that the modified geodesic models of QPOs can explain the observational fixed data from the microquasars and AGNs but not for all sources. We perform a successful fitting of the high frequency QPOs models of epicyclic resonance and its variants, relativistic precession and its variants, tidal disruption, as well as warped disc models, and discuss the corresponding constraints of parameters of the model, which are the spin of the test particle, mass and rotation of the BH.

Frugal Method of Notch Modification of Scleral Contact Lenses in the Setting of Complex Ocular Surface Anatomy.

Scleral contact lenses (ScCLs) have gained popularity as a treatment of refractive errors in patients with complex anterior segment pathology. Patients with mechanical abnormalities of the ocular surface may be unsuccessful with traditional ScCL fitting. Scleral contact lens modifications, such as notching and microvaulting, typically incur additional financial costs and require the services of professional laboratories. We describe a frugal method of ScCL notch modification that can be performed by a practitioner using readily available tools in a single office visit. Two patients with abnormal ocular surface anatomy were fit with the practitioner-modified ScCL and achieved successful visual rehabilitation. We offer this method as a potentially economical and effective technique to achieve successful ScCL fitting in this challenging patient population with pathologies that may preclude standard ScCL usage.

A predictive model of choosing pessary type for women with symptomatic pelvic organ prolapse.

Objective:To investigate clinical factors including translabial ultrasound parameters, which are predictive for choosing pessary type (Ring or Gellhorn) in the fitting trial, and to establish a predictive model.Methods:A retrospective study was conducted on symptomatic women with pelvic organ prolapse (POP) at the Pelvic Floor Disease Diagnosis and Treatment Center (Liaoning Province, China) between May 2018 and December 2020 who were successfully fitted with pessaries. This retrospective study was supplemented with a prospective cohort study on women seeking pessary for first-line treatment of POP at the above tertiary center between December 2020 and April 2021 for validation. Enrolled participants were grouped by their fitted type of pessary. Demographic and clinical parameters between groups, including pelvic organ prolapse quantification and translabial ultrasound, were analyzed using logistic regression. A receiver operating characteristic curve was calculated using predictive values obtained by regression as the predictor for choosing pessary type in the pessary fitting trial.Results:The 181 participants included in the retrospective analysis were randomly divided into the “Development” and “Validation” datasets. In the “Development” set, multivariable logistic regression analyses showed that a younger age (odds ratio [OR]: 0.950; 95% confidence interval [CI]: 0.908-0.995; P = 0.026), a larger hiatal circumference on Valsalva (OR: 1.348; 95% CI: 1.103-1.647; P = 0.004), and a higher POP-Q stage (OR: 2.963; 95% CI: 1.210-7.255; P = 0.017) were independent predictors for successful fitting with the Gellhorn pessary. The predictive model was P = exp(Z)/[1 + exp(Z)], Z = −0.051 × Age (y) + 0.298 × hiatal circumference on Valsalva (cm) + 1.086 × pelvic organ prolapse stage (2, 3, or 4) − 5.490. The area under the receiver operating characteristic curves (AUC) was 0.776 (P < 0.001) and 0.705 (P < 0.001) based on the “Development” dataset and “Validation” datasets, respectively. The AUC was 0.815 (P < 0.001) based on the prospective cohort validation.Conclusions:For severe POP, women with younger age and larger hiatal circumference, Gellhorn pessaries should be their first choice instead of ring ones in pessary fitting trials.

Panel Optimization for High-Dimensional Immunophenotyping Assays Using Full-Spectrum Flow Cytometry.

Technological advancements in fluorescence flow cytometry and an ever-expanding understanding of the complexity of the immune system have led to the development of large flow cytometry panels reaching up to 43 colors at the single-cell level. However, as panel size and complexity increase, so too does the detail involved in designing and optimizing successful high-quality panels fit for downstream high-dimensional data analysis. In contrast to conventional flow cytometers, full-spectrum flow cytometers measure the entire emission spectrum of each fluorophore across all lasers. This allows for fluorophores with very similar emission maxima but unique overall spectral fingerprints to be used in conjunction, enabling relatively straightforward design of larger panels. Although a protocol for best practices in full-spectrum flow cytometry panel design has been published, there is still a knowledge gap in going from the theoretically designed panel to the necessary steps required for panel optimization. Here, we aim to guide users through the theory of optimizing a high-dimensional full-spectrum flow cytometry panel for immunophenotyping using comprehensive step-by-step protocols. These protocols can also be used to troubleshoot panels when issues arise. A practical application of this approach is exemplified with a 24-color panel designed for identification of conventional T-cell subsets in human peripheral blood. © 2021 Malaghan Institute of Medical Research, Cytek Biosciences. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Preparation and evaluation of optimal spectral reference controls Support Protocol 1: Antibody titration Support Protocol 2: Changing instrument settings Basic Protocol 2: Unmixing evaluation of fully stained sample Basic Protocol 3: Evaluation of marker resolution Support Protocol 3: Managing heterogeneous autofluorescence Basic Protocol 4: Assessment of data quality using expert gating and dimensionality reduction algorithms.

Adsorbate-adsorbate interactions on microporous materials

Simple isotherm models can fit microporous adsorption yet the molecular interactions underlying the successful fitting have often remained obscure. Here we demonstrate how semi-empirical isotherm model data can be mined to reveal the reality of adsorbate-adsorbate molecular interactions. This was made possible by the fluctuation adsorption theory, a rigorous theory based only on the principles of statistical thermodynamics. For microporous carbons, adsorbate-adsorbate interactions quantified from the Dubinin-Radishkevich (DR) and Dubinin-Astakhov (DA) models successfully capture the primary micropore filling mechanism and the subsequent layer adsorption, leading to a liquid-like behaviour of the adsorbates. The microscopic meanings of the DR and DA parameters and the adsorption potential have also been clarified via statistical thermodynamics. • A novel statistical thermodynamic approach to adsorption has been developed. • Adsorbate-adsorbate interaction can be quantified from semi-empirical isotherm models. • Molecular basis of Dubinin-Radishkevich and Dubinin-Astakhov models clarified. • Adsorbate-adsorbate interactions support the proposed adsorption mechanisms. • Physical meaning of the “adsorption potential” was clarified.

Fermion masses and mixings in a U(1)X model based on the Σ(18) discrete symmetry

Abstract We have built a renormalizable $U(1)_X$ model with a $\Sigma (18)\times Z_4$ symmetry, whose spontaneous breaking yields the observed standard model (SM) fermion masses and fermionic mixing parameters. The tiny masses of the light active neutrinos are produced by the type I seesaw mechanism mediated by very heavy right-handed Majorana neutrinos. To the best of our knowledge, this model is the first implementation of the $\Sigma (18)$ flavor symmetry in a renormalizable $U(1)_X$ model. Our model allows a successful fit for the SM fermion masses, fermionic mixing angles, and CP phases for both quark and lepton sectors. The obtained values for the physical observables of both quark and lepton sectors are in accordance with the experimental data. We obtain an effective neutrino mass parameter of $\langle m_{ee}\rangle=1.51\times 10^{-3}\, \mathrm{eV}$ for normal ordering (NO) and $\langle m_{ee}\rangle =4.88\times 10^{-2} \, \mathrm{eV}$ for inverted ordering (IO), which are well consistent with the recent experimental limits on neutrinoless double beta decay.

Identifying Controlling Factors of Bioaccumulation of Selected Metal(loid)s in Various Soil–Cereal Crop Systems within Cultivated Fluvisols

The paired Fluvisol and cereal samples in both the field screening and controlled experiments are reported to elucidate the soil–crop relationship for As, Cd, and Pb in relation to changing contamination levels. Significant varietal differences in plant uptake were observed for crop type (barley, triticale) and the harvested part of the crop (oat shoots and grain). When parametrizing the stepwise regression models, the inclusion of soil properties often improved the performance of soil–crop models but diverse critical soil parameters were retained in the model for individual metal(loid)s. The pH value was often a statistically significant variable for Cd uptake. For As and Pb, the more successful model fit was achieved using the indicators of quantity or quality of soil organic matter, but always with lower inherent model reliability compared to Cd. Further, a single correlation analysis was used to investigate the relationship between extractable metal concentrations in soil solution and their crop accumulation. For Cd, there were strong intercorrelations among single extractions, the NH4NO3 extraction stood out with perfect correlation with plant uptake in both experiments. For As and Pb, the CaCl2 and Na2EDTA solutions outperformed other single extractions and were the better choice for the assessment of depositional fluvial substrates.

Clinical Outcome of Transfemoral Direct Socket Interface (Part 2).

Amputation at the transfemoral (TF) level reduces the rate of successful prosthetic fitting, functional outcome, and quality of life (QoL) compared with transtibial amputation. The TF socket interface is considered the most critical part of the prosthesis, but socket discomfort is still the most common user complaint. Direct Socket for transfemoral prosthesis users is a novel interface fabrication process where the socket is shaped and laminated directly on the residual limb and delivered in a single visit. The aim of this study was to investigate if prosthetic users' quality of life (QoL), comfort, and mobility with a Direct Socket TF interface were comparable to their experience with their previous prostheses. The pre/post design prospective cohort study included 47 subjects. From this cohort, 36 subjects completed the 6-months follow-up (mean age 58 years, 27 males). Outcomes at baseline included EQ-5D-5L®, PLUS-M™, CLASS, ABC, AMPPRO, and TUG. At 6-weeks and 6-months, subjects repeated all measures. Seven Certified Prosthetist (CP) investigators performed observations and data collection at six different sites (from July 2018 to April 2020). Results showed significant improvement in all outcome measures for the 36 subjects that completed both 6-weeks and 6-months follow-ups. CLASS sub-scales showed significantly improved stability, suspension, comfort, and socket appearance. Improvement in K-Level and less use of assistive devices were observed with the AMPPRO instrument, indicating improved user mobility and performance. QoL was also increased, as measured in Quality-Adjusted-Life-Years (QALY) from the EQ-5D-5L. Evidence from the findings demonstrate that the Direct Socket TF system and procedure can be a good alternative to the traditional method of prosthetic interface delivery.

A fast MR-thermometry method for quantitative assessment of temperature increase near an implanted wire.

To propose a MR-thermometry method and associated data processing technique to predict the maximal RF-induced temperature increase near an implanted wire for any other MRI sequence. A dynamic single shot echo planar imaging sequence was implemented that interleaves acquisition of several slices every second and an energy deposition module with adjustable parameters. Temperature images were processed in real time and compared to invasive fiber-optic measurements to assess accuracy of the method. The standard deviation of temperature was measured in gel and in vivo in the human brain of a volunteer. Temperature increases were measured for different RF exposure levels in a phantom containing an inserted wire and then a MR-conditional pacemaker lead. These calibration data set were fitted to a semi-empirical model allowing estimation of temperature increase of other acquisition sequences. The precision of the measurement obtained after filtering with a 1.6x1.6 mm2 in plane resolution was 0.2°C in gel, as well as in the human brain. A high correspondence was observed with invasive temperature measurements during RF-induced heating (0.5°C RMSE for a 11.5°C temperature increase). Temperature rises of 32.4°C and 6.5°C were reached at the tip of a wire and of a pacemaker lead, respectively. After successful fitting of temperature curves of the calibration data set, temperature rise predicted by the model was in good agreement (around 5% difference) with measured temperature by a fiber optic probe, for three other MRI sequences. This method proposes a rapid and reliable quantification of the temperature rise near an implanted wire. Calibration data set and resulting fitting coefficients can be used to estimate temperature increase for any MRI sequence as function of its power and duration.

Prospective observational study of gender and ethnicity biases in respiratory protective equipment for healthcare workers in the COVID-19 pandemic

ObjectiveTo describe success rates of respiratory protective equipment (RPE) fit testing and factors associated with achieving suitable fit.DesignProspective observational study of RPE fit testing according to health and safety, and...

Improved method for post-processing correction of B1 inhomogeneity in glutamate-weighted CEST images of the human brain.

Glutamate-weighted CEST (gluCEST) imaging is nearly unique in its ability to provide non-invasive, spatially resolved measurements of glutamate in vivo. In this article, we present an improved correction for B1 inhomogeneity of gluCEST images of the human brain. Images were obtained on a Siemens 7.0 T Terra outfitted with a single-volume transmit/32-channel receive phased array head coil. Numerical Bloch-McConnell simulations, fitting and data processing were performed using in-house code written in MATLAB and MEX (MATLAB executable). "Calibration" gluCEST data was acquired and fit with a phenomenological functional form first described here. The resulting surfaces were used to correct experimental data in accordance with a newly developed method. Healthy volunteers of varying ages were used for both fitted "calibration" data and corrected "experimental" data. Simulations allowed us to describe the dependence of CEST at 3.0 ppm (gluCEST) on saturation B1 using a new functional form, whose validity was confirmed by successful fitting to real human data. This functional form was used to parameterize surfaces over the space (B1 , T1 ), which could then be used to correct the signal from each pixel. The resulting images show less signal loss in areas of low B1 and greater contrast than those generated using the previously published method. We demonstrate that, using this method with appropriate nominal saturation B1 , the major limitation of correcting for B1 inhomogeneity becomes the effective flip angle of the acquisition module, rather than inability to correct for inhomogeneous saturation. The lower limit of our correction ability with respect to both saturation and acquisition B1 is about 40% of the nominal value. In summary, we demonstrate a more rigorous and successful approach to correcting gluCEST images for B1 inhomogeneity. Limitations of the method and further improvements to enable correction in regions with severe pathology are discussed.

Characterization of Hydration Behaviour and Modeling of Film Formulation

Hydration behavior of hydrogel-based polymeric film possesses great importance in mucosal drug delivery. Modified Lag phase sigmoid model was used for the investigation of hydration of the film. Kaolin incorporated HPMC K100LVCR (HL) and K100M (HH) films containing dexamethasone as a model drug have been prepared for studying swelling kinetics. Swelling of HL and HH films was decreased with the gradual increase of kaolin content and HH of higher viscosity has shown higher value than HL matrix. Kaolin also inhibited the film erosion process. Mathematically modified lag phase sigmoid model demonstrated similarity of the predicted swelling content with the observed value. High R2 and small RMSE value confirmed the successful fitting of the modified lag phase sigmoid model to the experimental data of swelling content. τ value similar to the observed one was obtained. This modified model could be reliable enough for estimating hydration process in food grains, food packaging films etc.

Osseointegrated Implants for Orbito-Facial Prostheses: Common Complications and Solutions.

To evaluate anatomical and functional results of osseointegration with magnetic coupling for oculofacial prosthetic rehabilitation after exenteration. This retrospective study included 11 consecutive patients who received orbital reconstruction and oculofacial prosthetic rehabilitation between September 2015 and October 2019. Patient demographics, surgical indications, previous treatment procedures, histopathologic features, and reconstructive procedures were recorded. The mean age was 37.81 ± 23 years (range 5-78 years). The mean follow-up was 23.81 ± 12 months (range 10-48 months). The principal diagnoses were squamous cell carcinoma of the eyelids (n = 2/11), mucoepidermoid carcinoma of the maxillary sinus (n = 2/11), rhabdomyosarcoma (n = 1/11), mucormycosis (n = 1/11), neurofibromatosis (n = 1/11), basosquamous carcinoma (n = 1/11), malign melanoma (n = 1/11), primitive neuroectodermal tumor (n = 1/11), and retinoblastoma (n = 1/11). Six of the patients were repaired by primary closure. Procedures performed to reconstruct the orbital cavity included split-thickness skin graft (n = 2/11), temporalis muscle flap (n = 2/11), and frontalis muscle flap (n = 1/11). Nine of the 11 patients who received orbital implants were successfully rehabilitated by epithesis. Postoperative complications included implant loss (n = 4/11), periprosthetic local infection (n = 3/11), and soft tissue overgrowth around the orbital prosthesis (n = 2/11). All patients had Straumann bone level implant (Basel, Switzerland) osseointegrated titanium implants (3.5 mm) placed in a 2-stage procedure over a span of 3 to 4 months with subsequent successful prosthesis fitting. The reconstructive methods following orbital exenteration, should be customized according to the patients' characteristics such as extension of the orbital defect, bone quality, and expectations to achieve satisfactory results.

Leveraging the Coronavirus Disease 2019 Pandemic: Is It Time to Consider Incorporating Mobile Applications Into Standard Clinical Management of the Liver Transplantation Patient?

Over the past decade, major advancements in the development of mobile applications and telehealth monitoring systems have assisted healthcare professionals in the diagnosis and management of chronic disease. When effectively used, mobile applications can lead to higher quality care and better patient-reported outcomes.(1) Mobile applications can also improve patient self-management of chronic metabolic disease.(2) Despite these known benefits in other chronic diseases, telehealth and mobile applications have been slow to be adopted in standard clinical management of the liver transplant patient, in-part due to the complexity of chronic liver disease where there is often a need for physical examination, physical frailty assessment, support network determination and building rapport.(3).

Determination of bulk and surface properties of liquid Bi-Sn alloys using an improved quasi-lattice theory

Abstract The thermodynamic properties of Bi-Sn were studied at 600 and 900 K using a quasi-lattice theory. After successful fitting of Gibbs free energies of mixing and thermodynamic activities, the fitting parameters were used to investigate the enthalpy of mixing, the entropy of mixing, concentration fluctuations, Warren-Cowley short-range-order parameter, surface concentrations and surface tensions of the binary systems. Positive and symmetrically shaped enthalpies of mixing were observed in all composition range, while negative excess entropies of mixing were observed. Bi-Sn showed a slight preference for like-atoms as nearest neighbours in all composition range. The nature of atomic order in Bi-Sn at 600 and 900 K appeared similar. The highest tendency for homocoordination exists at composition where mole fraction of Bi is about 40%. It was also observed that Bi (whose surface tension is lower than that of Sn) has the highest surface enrichment in the Bi-Sn systems. Unlike many previous applications of the quasi-lattice theory where constant values were used to approximate coordination numbers, temperature and composition-dependent coordination numbers were applied in this work.