Wetting of soap bubbles on topographic surfaces.

HYPOTHESIS: There is a relationship between the static contact angle of droplets and soap bubbles on flat homogeneous surfaces, therefore, it should be possible to derive a relationship between the static contact angle of a soap bubble on a periodic topographic surface and a droplet on a flat homogeneous surface. EXPERIMENTS: A free energy model of the static contact angle of soap bubbles on a topographic surface in the Cassie-Baxter state was derived. Polydimethylsiloxane surfaces of varying area fraction (0.125, 0.250, 0.500, 0.750, and 1.00) and periodic topographies (lined and pillared) were fabricated using 3D printed moulds for pattern transfer. A bubble goniometer was developed to accommodate bubbles of 40,000 ± 5,000 mm3 and 50,000 ± 5,000 mm3 volumes. Then, the static contact angle of bubbles of both volumes were measured on the varying topographic surfaces. FINDINGS: The derived predictions imply that the relationship between the static contact angle for bubbles on a flat homogeneous surface and on a composite surface, has the same form as the Cassie-Baxter equation for a droplet. The experimental results for the measured static contact angle for both bubble volumes on the varying surfaces had good agreement with the predicted trends.

Effects of Aging on Patellofemoral Joint Stress during Stair Negotiation on Challenging Surfaces.

This study examined the effect of age and surface on patellofemoral joint (PFJ) stress magnitude and waveform during stair ascent and descent tasks. A total of 12 young and 12 older adults had knee biomechanics quantified while they ascended and descended stairs on normal, slick, and uneven surfaces. The peak of stance (0-100%) PFJ stress and associated components were submitted to a two-way repeated measures ANOVA, while the PFJ stress waveform was submitted to statistical parametric mapping two-way ANOVA. During stair ascent, older adults exhibited greater PFJ stress waveforms, from 55 to 59% and 74 to 84% of stance (p < 0.001) as well as greater PFJ stress-time integral across stance (p = 0.003), and later peak PFJ stress, than young adults (p = 0.002). When ascending on the uneven surface, participants exhibited smaller PFJ stress from 9 to 24% of stance compared to the normal surface, but greater PFJ stress from 75 to 88% and from 63 to 68% of stance (p < 0.001) as well as greater PFJ stress-time integrals compared to normal and slick surfaces (p < 0.032). During stair descent, older adults exhibited a smaller PFJ contact area range (p = 0.034) and peak knee flexion angle (p = 0.022) than young adults. When descending on the slick surface, participants exhibited smaller PFJ stress from 5 to 18% of stance, but greater stress, from 92 to 98% of stance (both: p < 0.001), compared to the normal surface. Negotiating slick and uneven stairs may produce knee biomechanics that increase PFJ stress, and the larger, later PFJ stress exhibited by older adults may further increase their risk of PFJ pain.

Imaging magnetic spiral phases, skyrmion clusters, and skyrmion displacements at the surface of bulk Cu2OSeO3.

Surfaces - by breaking bulk symmetries, introducing roughness, or hosting defects - can significantly influence magnetic order in magnetic materials. Determining their effect on the complex nanometer-scale phases present in certain non-centrosymmetric magnets is an outstanding problem requiring high-resolution magnetic microscopy. Here, we use scanning SQUID microscopy to image the surface of bulk Cu2OSeO3 at low temperature and in a magnetic field applied along 100 . Real-space maps measured as a function of applied field reveal the microscopic structure of the magnetic phases and their transitions. In low applied field, we observe a magnetic texture consistent with an in-plane stripe phase, pointing to the existence of a distinct surface state. In the low-temperature skyrmion phase, the surface is populated by clusters of disordered skyrmions, which emerge from rupturing domains of the tilted spiral phase. Furthermore, we displace individual skyrmions from their pinning sites by applying an electric potential to the scanning probe, thereby demonstrating local skyrmion control at the surface of a magnetoelectric insulator.

Discontinuity-enhanced icephobic surfaces for low ice adhesion.

HYPOTHESIS: Passive low ice-adhesion surfaces are frequently composed of soft materials; however, soft materials potentially present durability issues, which could be overcome by fabricating composite surfaces with patterned rigid and soft areas. Here we propose the innovative concept of discontinuity-enhanced icephobic surfaces, where the stress concentration at the edge between rigid and soft areas, i.e. where discontinuities in elasticity are located, facilitates ice detachment. EXPERIMENTS: Composite model surfaces were fabricated with controlled rigid-soft ratios and discontinuity line lengths. The ice adhesion values were measured while recording the ice/substrate interface, to unravel the underpinning ice detachment mechanism. The experiments were complemented by numerical simulations that provided a better understanding of the ice detachment mechanism. FINDINGS: It was found that when a surface contains rigid and soft areas, stress is concentrated at the edge between soft and hard areas, i.e. at the discontinuity line, rather than all over the soft or rigid areas. An unexpected non-unidirectional crack propagation was observed for the first time and elucidated. When rigid and deformable materials are present, the crack occurs on the discontinuity line and propagates first on rigid and then on soft areas. Moreover, it was demonstrated that an increase in discontinuities promotes crack initiation and leads to a reduction of ice adhesion.

Design and study of additively manufactured Three periodic minimal surface (TPMS) structured porous titanium interbody cage.

Objective: TPMS porous structures have adjustable stiffness, a smooth surface, and highly connected pores, which help avoid stress concentration within the dot-matrix structure and promote cell adhesion and proliferation. A cervical interbody cage based on this type of porous structure was designed and fabricated, and its mechanical properties and biocompatibility were evaluated. Methods: TPMS porous structures have adjustable stiffness, a smooth surface, and highly connected pores, which help avoid stress concentration within the dot-matrix structure and promote cell adhesion and proliferation. A cervical interbody cage based on this type of porous structure was designed and fabricated, and its mechanical properties and biocompatibility were evaluated. Results: The volume fraction of the 3D-printed TC4-based Tubular-G structure was linearly related to compressive strength. Adjusting the volume fraction resulted in a Tubular-G structure with a modulus and yield strength similar to human bone, without stress concentration within the structure. The designed and fabricated TC4-based Tubular-G porous cervical interbody cage demonstrated excellent anti-sagging properties and biocompatibility. Conclusions: The volume fraction of the 3D-printed TC4-based Tubular-G structure was linearly related to compressive strength. Adjusting the volume fraction resulted in a Tubular-G structure with a modulus and yield strength similar to human bone, without stress concentration within the structure. The designed and fabricated TC4-based Tubular-G porous cervical interbody cage demonstrated excellent anti-sagging properties and biocompatibility.

Leaf abaxial and adaxial surfaces differentially affect the interaction of Botrytis cinerea across several eudicots.

Eudicot plant species have leaves with two surfaces: the lower abaxial and the upper adaxial surface. Each surface varies in a diversity of components and molecular signals, resulting in potentially different degrees of resistance to pathogens. We tested how Botrytis cinerea, a necrotroph fungal pathogen, interacts with the two different leaf surfaces across 16 crop species and 20 Arabidopsis genotypes. This showed that the abaxial surface is generally more susceptible to the pathogen than the adaxial surface. In Arabidopsis, the differential lesion area between leaf surfaces was associated with jasmonic acid (JA) and salicylic acid (SA) signaling and differential induction of defense chemistry across the two surfaces. When infecting the adaxial surface, leaves mounted stronger defenses by producing more glucosinolates and camalexin defense compounds, partially explaining the differential susceptibility across surfaces. Testing a collection of 96 B. cinerea strains showed the genetic heterogeneity of growth patterns, with a few strains preferring the adaxial surface while most are more virulent on the abaxial surface. Overall, we show that leaf-Botrytis interactions are complex with host-specific, surface-specific, and strain-specific patterns.

Design Aspects in Vat Photopolymerization Additive Manufacturing of Hydrophobic Surfaces.

Hydrophobic surfaces require finely tuned process chains due to the scale, complexity, and patterning methods. For this purpose, vat photopolymerization (VPP) additive manufacturing is a promising method for surface generation; however, together with the fabrication process, the design phase needs to be optimized to achieve the desired surface property. This work presents the influence of the design features of hydrophobic surfaces through multiple studies on simple pillar structures, intrinsic single-unit geometries, and surface deposition on complex substrates. The results showed that depending on the dimensions of single pillar dimensions, wetting properties can extend between the contact angles (CA) of 83°-115.11°. The hydrophobicity was further increased by applying a re-entrant structure, reaching the CA of 115.24°. The surface deposition on the complex substrates significantly increased water droplet adhesion, preventing it from rolling off, which can be beneficial for manifold device protection from the hazardous influence of the environment. In addition, the influence of the surface on the acoustic properties was examined, which showed that the pattern application in the real-life device does not have a detrimental effect on the intrinsic functionality. This study showed that the design phase should be an essential part of the VPP process chain as it significantly influences the wetting properties of the surfaces.

Effectiveness of intensive motor learning approaches from working on a vertical surface on hemiplegic children's upper limb motor skills, a randomized controlled trial.

PURPOSE: This study compares the effect of intensive motor learning approaches on improving the quality of upper extremity skills in children with unilateral cerebral palsy (UCP) by working on vertical surfaces versus horizontal surfaces during rehabilitation sessions. MATERIALS AND METHODS: Forty UCP children of both sexes were randomized into two equal groups. All participants received 60 min of intensive motor learning approaches three days/week for three successive months. These approaches included constraint-induced movement therapy (CIMT), in which children wore a splint or sling on the unaffected upper limb, as well as hand-arm bimanual intensive training (HABIT) that requires the use of both hands during specific play-based activities. The control group received training on a horizontal surface while the child sat in front of an elbow-height table while the study group (vertical surface training) sat or stood in front of a wall/mirror/board. The task requirements were graded to ensure success. RESULTS: Statistically significant differences were detected between the mean values of post-treatment of all scorers, with a greater percentage of improvement in favor of the study group. CONCLUSIONS: This study revealed that working on a vertical surface improved upper limb motor skills more significantly than working on a horizontal surface.

This study compares the effect of intensive motor learning approaches on improving the quality of upper extremity skills in children with unilateral cerebral palsy by working on vertical surfaces versus horizontal surfaces during rehabilitation sessions.Incorporating occupational therapy tasks on a vertical surface may increase the control of proximal muscles and ease graphomotor performance.Working on a vertical surface can make activities fun for children and make challenging tasks, like writing, more interesting.Working on a vertical surface during rehabilitation sessions can particularly help children with unilateral cerebral palsy to further develop essential fine, visual, and gross motor skills more than training on horizontal surfaces.

Hydrodynamic frictional performance of fouled panels: a comparative study of different coating types.

This research study delves into the hydrodynamic frictional characteristics of fouled panels coated with different types of coatings, investigating how fouling coverage and surface roughness influence drag. The investigation incorporates data on the overall percentage coverage of fouling, as well as roughness measurements obtained through a 3D profilometer. Drag data collected from a flowcell simulation of real-world flow conditions complements these measurements. Notably, the determination of the level of fouling leverages the capabilities of CIE L*a*b as an image analysis method, focusing on the overall coverage rather than individual fouling species. The objective is to illustrate how fouled panels perform under varying flow and coating conditions compared to their clean counterparts. Furthermore, the paper proposes a roughness scaling approach that considers both the percentage coverage and measured areal roughness for each coating type, encompassing both fouled and unfouled areas. This approach provides valuable insights into the combined effects of fouling and surface roughness on hydrodynamic performance, enhancing our understanding of the intricate interplay between these factors.

Engaging the Concepts of Bimetallicity and Mechanical Strain for N2 Activation: A Computational Exploration.

N2 activation is a vital step in the process toward NH3 production. NH3 synthesis has been considered a crucial process for the production of value-added chemicals and/or hydrogen carriers over recent years. In this work, density functional theory (ab initio) calculations are implemented for a thorough screening of bimetallic alloy surfaces using Fe, Ru, and Mo as the matrix (host) metals and Ag, Au, Co, Cu, Fe, Mo, Ni, Pd, Pt, Rh, and Rh as heterometals toward exploring the N2 catalytic activation (electronic and chemical characteristics); the monometallic surfaces are used for critical comparison in terms of their N2 activation behavior. In particular, adsorption geometries/energetics, density of states (DOS), and charge transfer are discussed. From the N2 activation on the surfaces, we could precisely capture the transition state of the N2 dissociation reaction/step. The effect of the metal alloying (geometrical and electronic factors) as well as the effect of applied mechanical strain, as a tuning factor of alloying, are both studied and thoroughly discussed. DOS studies revealed that the d-band center moved toward the negative direction for all late-TM-based alloys, thereby allowing the nitrogen molecule to adsorb weakly as compared to the early-TM surface alloys. In terms of the mechanical strain, for most of the alloy surfaces studied, apart from the Mo/Fe(110) one, the N2 binding energy varies as a linear function of the applied strain. The mechanical effect trend is in agreement with the charge transfer descending order followed: Fe/Mo(110) > Rh/Mo(110) > Au/Mo(110) > Pt/Mo(110) > Ni/Mo(110) > Ru/Mo(110) > Cu/Mo(110) > Ag/Mo(110) > Pd/Mo(110) > Au/Mo(110), pointing out that Fe-functionalized Mo(110) surface presents the highest charge transfer of -2.14 |e| to the N2 molecule. This study aspires to provide navigation criteria through the abundant design criteria of N2 activation catalysts.

An analytical approach for determining contact angle hysteresis on smooth, micropillared, and micropored homogeneous surfaces.

HYPOTHESIS: Numerous theoretical models have been developed from various research perspectives, including free energy analysis, force balance, and contact line dynamics, to elucidate the contact angle hysteresis on solid surfaces, especially for superhydrophobic surfaces. However, these models can produce inconsistent predictions, and few of them account for contact angle hysteresis on smooth and microstructured surfaces simultaneously. THEORY: Formulas for advancing and receding free energy barriers of drops on different solid surfaces were derived, and then these formulas were simplified by incorporating the geometric constraint equation of drops, leading to an establishment of analytical models. FINDINGS: This study presented a unified approach for deriving analytical models of contact angle hysteresis for various wetting systems, including drops on smooth homogeneous surfaces, Cassie drops on micropillared and micropored homogeneous surfaces, and Wenzel drops on micropillared homogeneous surfaces. The established models revealed a significant impact of frictional tension, and of the change in free energy during drop motion, on the free energy barriers. These models were fully derived thermodynamically without subsequent theoretical modifications and found to agree well with experimental results. Some of the models in this study were validated using other existing models, despite the models having been developed using completely different approaches.

Dataset of Edmonds' bi-vectors and tri-vectors with realizations.

In 1965, Jack Edmonds characterized pairs of graphs G and G* with a bijection between their edge sets that form a pair of dual graphs realizing the vertices and countries of a map embedded in a surface. A necessary condition is that, if d = (d1, …, dn) and t = (t1,…, tm) denote the degree sequences of two such graphs, then ∑ i = 1 n d i = ∑ j = 1 m t j = 2 l , where l is the number of edges in each of the two graphs and χ = n + m - l is the Euler characteristic of the surface. However, this condition is not sufficient, and it is an open question to characterize bi-vectors (d, t) that are geographic, that is, that can be realized as the degree sequences of pairs G and G* of surface-embedded graphs. The above question is a special case of the following one. A multigraph G is even if each vertex has even degree and 3-colored if G is equipped with a fixed proper coloring of its vertex set assigning each vertex a color in the set {1,2,3}. Let G be a 3-colored even multigraph embedded in a surface S so that every face is a triangle. Denote by d = (d1, …, dn), t = (t1, …, tm), and δ = (δ1, ..., …, δk) the sequences of half-degrees of vertices of G of colors 1, 2, and 3, respectively. Then, ∑ i = 1 n d i = ∑ j = 1 m t j = ∑ µ = 1 k t µ = l , where χ = n + k + m - l is the Euler characteristic of the surface S. A tri-vector (d, t, δ) satisfying the above conditions is called feasible. A feasible tri-vector is called geographic if it is realized by a 3-colored triangulation of a surface. Geographic tri-vectors extend the concept of geographic bi-vectors. We present a dataset of geographic bi-vectors and tri-vectors, along with realizations proving that they are geographic.

Explant analysis of a chromium nitride coated metal-on-metal total wrist replacement: A case study.

Explant analysis can provide important understanding of how artificial joints perform in the human body. The articulating surfaces of the metacarpal head and the radius cup from a chromium nitride coated metal-on-metal Motec wrist implant were analysed. Due to bone resorption and aseptic loosening, the implant was removed after 6 years in the patient, and metallosis was observed during removal. Visually, some areas of the articulating surfaces appeared polished, others were dulled. A chemical composition analysis of the metacarpal head showed that the polished surfaces were chromium rich, implying this surface was the original chromium nitride coating, whereas the dulled surfaces were cobalt rich, indicating the underlying cobalt chromium substrate. In addition, the underlying cobalt chromium substrate was an order of magnitude rougher than the polished surface, indicating the scale of damage to it. It is speculated that the loss of the coating, and the subsequent damage to the underlying substrate due to a third-body wear process, led to osteolysis and the metallosis seen at revision surgery.

Unmasking Fluorinated Moieties on the Surface of Hydride-Terminated Silicon Nanoparticles.

Despite the widespread use of hydrofluoric acid (HF) in the preparation of silicon surfaces, the true nature of fluorinated surface species remains unclear. Here, we employ an array of characterization techniques led by solid-state nuclear magnetic resonance spectroscopy to uncover the nature of fluorinated moieties on the surface of hydride-terminated silicon nanoparticles (H-SiNPs). A structural model that explains the observed trends in 19F and 29Si magnetic shielding is proposed and further supported by quantum chemical computations. Fluorine is incorporated into local oxidation domains on the surface and clustered at the interface of the oxide and surrounding hydride-terminated surface. Silicon sites capped by a single fluorine are also identified by their distinct 19F and 29Si chemical shifts, providing insight into how fluorine termination influences the electronic structure. The extent of fluorine passivation and the effects of fluorine on the optical properties of SiNPs are also discussed. Finally, challenges associated with Teflon contamination are highlighted that future explorations of nanomaterials may have to contend with.

Barrier Membrane with Janus Function and Structure for Guided Bone Regeneration.

Guided bone regeneration (GBR) technology has been demonstrated to be an effective method for reconstructing bone defects. A membrane is used to cover the bone defect to stop soft tissue from growing into it. The biosurface design of the barrier membrane is key to the technology. In this work, an asymmetric functional gradient Janus membrane was designed to address the bidirectional environment of the bone and soft tissue during bone reconstruction. The Janus membrane was simply and efficiently prepared by the multilayer self-assembly technique, and it was divided into the polycaprolactone isolation layer (PCL layer, GBR-A) and the nanohydroxyapatite/polycaprolactone/polyethylene glycol osteogenic layer (HAn/PCL/PEG layer, GBR-B). The morphology, composition, roughness, hydrophilicity, biocompatibility, cell attachment, and osteogenic mineralization ability of the double surfaces of the Janus membrane were systematically evaluated. The GBR-A layer was smooth, dense, and hydrophobic, which could inhibit cell adhesion and resist soft tissue invasion. The GBR-B layer was rough, porous, hydrophilic, and bioactive, promoting cell adhesion, proliferation, matrix mineralization, and expression of alkaline phosphatase and RUNX2. In vitro and in vivo results showed that the membrane could bind tightly to bone, maintain long-term space stability, and significantly promote new bone formation. Moreover, the membrane could fix the bone filling material in the defect for a better healing effect. This work presents a straightforward and viable methodology for the fabrication of GBR membranes with Janus-based bioactive surfaces. This work may provide insights for the design of biomaterial surfaces and treatment of bone defects.

Lower Extremity Injury Rates on Artificial Turf Versus Natural Grass Surfaces in the National Football League During the 2021 and 2022 Seasons.

Background: It has been argued that the use of artificial turf football fields in the National Football League (NFL) increases player injury risk compared with natural grass surfaces. Purpose/Hypothesis: The purpose of this study was to quantify the rate of lower extremity injuries occurring in NFL players on artificial turf compared with natural grass surfaces and characterize the time missed due to injury and proportion of injuries requiring surgery. It was hypothesized that lower extremity injuries requiring surgical intervention would occur at a higher rate on artificial turf than on natural grass. Study Design: Descriptive epidemiology study. Methods: Lower extremity injury data for the 2021 and 2022 NFL seasons were obtained using publicly available records. Data collected included injury type, player position, player age, playing surface, weeks missed due to injury, and whether the patient underwent season-ending or minor surgery. Multivariable logistic regression was performed to determine the risk of season-ending surgery according to playing surface. Results: When combining injuries for the 2021 and 2022 seasons (N = 718 injuries), the incidence rate of lower extremity injury was 1.22 injuries/game for natural grass and 1.42 injuries/game for artificial turf. The odds of a season-ending surgery were found to be significantly higher on artificial turf compared with natural grass (odds ratio = 1.60; 95% CI, 1.28-1.99; P < .05), while additional variables, including weather, age, position, week of injury occurrence, and history of prior injury, did not influence the odds of season-ending surgery. Conclusion: The 2021 and 2022 NFL seasons of our analysis demonstrated a higher incidence rate of injuries on artificial turf surfaces compared with natural grass surfaces. In addition, the odds of injury requiring season-ending surgery were found to be significantly higher on artificial turf compared with natural grass.

Comparative Evaluation of Three Access Cavity Preparation Techniques on Root Canal Instrumentation Using Micro-CT: An In Vitro Study.

Background Access cavity preparation is a crucial step in nonsurgical root canal treatment. Recent advancements in access cavity designs focus on preserving maximum tooth structure while ensuring sufficient access to canal orifices for effective cleaning and shaping, resulting in minimally invasive procedures. However, there is limited information on the impact of three-dimensional (3D)-guided access cavity preparation in molars. A literature review found no prior studies comparing the effects of various access cavity preparation techniques on apical transportation, untouched surfaces, and debris formation within the canal. Objective The objective of this study is to compare and evaluate the effects of three different access cavity techniques on apical transportation, untouched surfaces, and debris formation within the root canal. Material and methods Thirty extracted permanent mandibular first molars were selected and randomly assigned to three groups for this study: Group I received 3D-printed static guided cavity preparation, Group II underwent conservative access cavity preparation, and Group III was subjected to traditional access cavity (TAC) preparation. The mesial canals in all samples were cleaned and shaped using TruNatomy files. Preoperative and postoperative micro-CT imaging was performed on each sample to assess the effects of the different access cavity preparation techniques on apical transportation, untouched surfaces, and debris formation within the root canal. Results The study found that Group I, which used 3D-printed static guided cavity preparation, exhibited significantly less apical transportation compared to Groups II and III, with mean differences of -0.1677 and -0.2079, respectively. Debris accumulation was similar across all groups, with mean values of 0.928 ± 0.824 for Group I, 0.751 ± 0.495 for Group II, and 0.938 ± 0.681 for Group III, indicating no significant impact of cavity preparation type on debris levels. For untouched canal surfaces, Group III (TAC preparation) had the fewest untouched surfaces, with mean differences of 3.0380 and 3.9020 compared to Groups II and I, respectively. Conclusions While TAC preparation reduces substantial tooth structure, it shows higher instrumentation efficacy and better cleaning of the root canal system. However, in complex cases where tooth structure preservation is crucial, guided access cavity preparation provides an effective balance between structural conservation and adequate canal access. This approach offers a tailored solution, optimizing treatment outcomes based on the specific clinical scenario.

Amyloid Proteins Adhesive for Slippery Liquid-Infused Porous Surfaces.

Biomimetic slippery liquid-infused porous surfaces (SLIPS) have emerged as a promising solution to solve the limitations of superhydrophobic surfaces, such as inadequate durability in corrosion protection and a propensity for frosting. However, the challenge of ensuring strong, lasting adhesion on diverse materials to enhance the durability of the lubricant layer remains. The research addresses this by leveraging amyloid phase-transitioned lysozyme (PTL) as an adhesive interlayer, conferring stable attachment of SLIPS across a variety of substrates, including metals, inorganics, and polymers. The silica-textured interface robustly secures the lubricant with a notably low sliding angle of 1.15°. PTL-mediated adhesion fortifies the silicone oil attachment to the substrate, ensuring the retention of its repellent efficacy amidst mechanical stressors like ultrasonication, water scrubbing, and centrifugation. The integration of robust adhesion, cross-substrate compatibility, and durability under stress affords the PTL-modified SLIPS exceptional anti-fouling, anti-icing, and anti-corrosion properties, marking it as a leading solution for advanced protective applications.

Monitoring the prevalence of Pseudomonas fluorescens as a spoilage indicator in cow raw milk, teat surfaces, and milk tanks.

Background: Milk and its products are very sensitive to spoilage if they are kept under unsuitable conditions which may provide favorable circumstances for the growth of specific spoilage organisms, Pseudomonas fluorescens accounted as the most dominant indicator for milk spoilage. Aim: This study highlights monitoring the prevalence of P. fluorescens as a spoilage indicator organism in cow raw milk and its contact surfaces represented by teat surfaces and milk tanks in Nineveh province. Methods: A total of 150 samples from cows' raw milk, teat surfaces, and milk tank swabs were collected from different locations in Nineveh province from October 2023 till February 2024. The Pseudomonas fluorescens were detected by using conventional cultivation methods supported by molecular detection of the target pathogen using the polymerase chain reaction technique. Results: Out of 150 samples, 48 (32%) were positive for the prevalence of P. fluorescens by traditional methods, and 39 (26%) were positive using PCR assay according to the 16SPflu gene yielded a band at 850 bp. The P. fluorescens was recovered at 19 (38%) from raw milk. Teat surfaces revealed a higher isolation rate 11 (22%) compared to milk tanks 9 (18%). The mean counts of Pseudomonas in cows raw milk revealed 4.38, 6.29, and 7.37 log CFU/ml for the 0, 3, and 6 days of storage at chilling temperature. Results of DNA sequencing of the 16SrRNA gene revealed 12 strains recorded in the GenBank nucleotide sequence database. Conclusion: Our results shed light on the risk of P. fluorescens prevalence as a spoilage indicator in raw milk and surrounding surfaces which is inevitable to apply hygienic procedures during milk collecting, processing, and preservation to increase the shelf life of the products and ensure milk safety and consumer health.

Targeted Energy Transfer Dynamics and Chemical Reactions.

Ultrafast reaction processes take place when resonant features of nonlinear model systems are taken into account. In the targeted energy or electron transfer dimer model this is accomplished through the implementation of nonlinear oscillators with opposing types of nonlinearities, one attractive while the second repulsive. In the present work, we show that this resonant behavior survives if we take into account the vibrational degrees of freedom as well. After giving a summary of the basic formalism of chemical reactions we show that resonant electron transfer can be assisted by vibrations. We find the condition for this efficient transfer and show that in the case of additional interaction with noise, a distinct non-Arrhenius behavior develops that is markedly different from the usual Kramers-like activated transfer.