Commercial Vacuum Research Articles

Enhancing Efficiency in Meniscal Repair: A Novel In-House Vacuum Suction Technique for Suture Loading in Long Hollow Needles and Devices.

Suture-loaded long hollow needles are used in arthroscopic surgery to pass or retrieve sutures and in meniscal repair surgeries. However, manual suture loading can be time-consuming and challenging, especially with finer sutures. We present a novel technique using vacuum suction to simplify and expedite suture loading in hollow needles and similar devices. Following ethical approval and participant consent, four healthcare professionals (one senior consultant, two junior consultants, and one trained operating theatre technician) attempted to load 16G and 18G needles, as well as free and double-loaded commercial anchor drivers, using manual and vacuum suction techniques. The best of three attempts was recorded for each participant. Loading times were compared using permutation tests, and inter-operator variability was analyzed via F-tests. Across all devices, the suction method reduced loading times significantly compared to manual loading, with times dropping to 2-4 seconds. The senior consultant required 15 seconds for manual loading, while the untrained junior consultant took up to 60 seconds. Permutation tests revealed statistically significant time reductions with suction loading (p = 0.0286 for all devices). F-tests showed a substantial decrease in variability with suction loading, confirming greater consistency across users. Vacuum suction is a quick, economical, and effective technique for loading sutures into long hollow needles and other devices. It not only drastically reduces loading times but also improves consistency across different users, making it a reliable technique for arthroscopic procedures. This method can potentially be applied to various surgical instruments, improving procedural efficiency and outcomes.

Numerical performance investigation of High Vacuum Flat Plate Hybrid Photovoltaic-Thermal devices.

We propose an innovative flat plate hybrid Photovoltaic-Thermal system under high vacuum (HV PV-T) optimized for solar-to-thermal energy conversion. It consists of a glass cover, metallic vessel, and the actual PV-T device, which englobes a low-emissive Transparent Conductive Oxide (TCO), a perovskite-based PV cell, a Solar Absorber, and a copper substrate. We investigate, through a 1-D model developed in MATLAB, the performances of the proposed PV-T system, still mined by radiative losses, varying the operating temperature (Top) and the emittance of the TCO (εTCO ) in the ranges of (25÷175) °C and (0.05÷0.45) respectively. The annual thermal and electrical productions are evaluated considering the Typical Meteorological Year of Naples, Italy. Specific annual costs and emission savings are evaluated and compared with the ones assured by commercial High Vacuum Flat Plate Solar-Thermal (HVFP ST) and PV collectors. Results indicate that the proposed HV PV-T increases the annual cost savings by 34% and 11% when compared to HVFP ST and PV collectors, respectively. Moreover, the presented HV PV-T increases the annual CO2 emissions savings by 7% and 48% when compared to HVFP ST and PV collectors, respectively.

Formation mechanism of white layer on a martensitic stainless steel and its effect on corrosion resistance

1Cr17Ni2 martensitic stainless steel has good corrosion resistance and mechanical properties, and thus it is widely used in corrosion-resistant and load-bearing parts. After the machining process, commercial 1Cr17Ni2 steel components are usually solution treated and tempered under vacuum condition to achieve higher strength as well as dimensional accuracy. However, severe premature corrosion of 1Cr17Ni2 steel components is always correlated with a white layer formed during the heat-treatment process on the surface. In this study, the 1Cr17Ni2 alloy samples were solution treated at 950 °C for 90 min by practical commercial vacuum furnace with the pressure of 13.3–26.6 Pa, followed by furnace cooling instead of oil quenching. The microstructure and local elemental distribution of the white layer on the surface of a 1Cr17Ni2 steel were characterized in detail by scanning electron microscopy, backscattered electron diffraction, scanning transmission electron microscopy and three-dimensional atomic probe. The sample surface transformed to a ∼15 µm thick white layer of austenite phase with fine particles rich in Cr and C atoms, which is different from the inner matrix containing a mixture of martensite and δ-ferrite. Elemental distribution showed a depletion of Cr and enrichment of C atoms in white layer compared with the matrix. This could expand the austenitic region, resulting in retained austenitic microstructure on the surface. In addition, since Cr elements were consumed locally, the corrosion resistance of the steel with white layer decreased significantly, as proved by salt spray test and intergranular corrosion resistance test. These microstructure observations and the elements distribution were interpreted consistently by carburizing from the contaminated commercial vacuum furnace.

Acoustic Attenuation Performance Analysis and Optimisation of Expansion Chamber Coupled Micro-perforated Cylindrical Panel Using Response Surface Method

This paper describes boundary element method (BEM), experimental and optimization studies conducted to understand the potential of expansion tube coupled micro-perforated cylindrical panel (MPCP) to enhance the acoustic attenuation for in-duct noise control issues. Due to complex structure of the MPCP and for the correct prediction of acoustic attenuation, BEM is adopted on the basis of PLM Simcenter 3D software to compute the sound transmission loss (TL). As the MPCP is cylindrical in-shape with numbers of sub-milimeter holes, additive manufacturing based 3D printing was utilized for the model prototyping to reduce current design limitation and enabled fast fabrication. The TL measurement based two-load method is adopted for modal validation. Subsequently, a parametric studies of the MPCP concerning the perforation hole diameter, perforation ratio and depth of air space are carried out to investigate the acoustical performance. Optimization via response surface method (RSM) is used as it allows evaluating the effects of multiple parameters as required in this study. The model validation result shows that the error between the BEM and and measured values is relatively small and show a good agreement. The R-square value is 0.89. The finding from parametric study shows that a widen peak attenuation can be achieve by reducing the perforation hole diameter and one way to increase the transmission loss amplitude is by increasing the air cavity depth. Finally, the optimized MPCP model was adopted to the commercial vacuum cleaner for the verification. The sound pressure level (SPL) of the vacuum cleaner is significantly attenuated within the objective frequency of 1.7 kHz and its A-weighted SPL is reduced by 1.8 dB.

SAR-AD Method to Characterize Eight SARA Fractions in Various Vacuum Residues and Follow Their Transformations Occurring during Hydrocracking and Pyrolysis

Model compounds were used to provide some chemical boundaries for the eight-fraction SAR-ADTM characterization method for heavy oils. It was found that the Saturates fraction consists of linear and highly cyclic alkanes; the Aro-1 fraction consists of molecules with a single aromatic ring; the Aro-2 fraction consists of mostly 2 and 3-ring fused aromatic molecules, the pericondensed 4-ring molecule pyrene, and molecules with 3–5 rings that are not fused; and the Aro-3 fraction consists of 4-membered linear and catacondensed aromatics, larger pericondensed aromatics, and large polycyclic aromatic hydrocarbons. The Resins fraction consists of mostly fused aromatic ring systems containing polar functional groups and metallated polar vanadium oxide porphyrin compounds, and the Asphaltene fraction consists of both island- and archipelago-type structures with a broad range of molecular weight variation, aromaticity, and heteroatom contents. The behavior of the eight SAR-ADTM fractions during hydrocracking and pyrolysis was investigated, and quantitative relations were established. Intercriteria analysis and evaluation of SAR-ADTM data of hydrocracked vacuum residue and sediment formation rate in commercial ebullated bed vacuum residue hydrocracking were performed. It showed that total asphaltene content, toluene-soluble asphaltenes, and colloidal instability index contribute to sediment formation, while Resins and Cyclohexane-soluble asphaltenes had no statistically meaningful relation to sediment formation for the studied range of operation conditions.

Commercial Ebullated Bed Vacuum Residue Hydrocracking Performance Improvement during Processing Difficult Feeds

The Urals and Siberian vacuum residues are considered difficult to process in the ebullated bed hydrocracking because of their increased tendency to form sediments. Their achievable conversion rate reported in the literature is 60%. Intercriteria analysis was used to assess data from a commercial vacuum residue hydrocracker during processing blends from three vacuum residues: Urals, Siberian Light, and Basra Heavy. The analysis revealed that the main contributors to conversion enhancement is hydrodemetallization (HDM) and the first reactor ΔT augmentation. The increase of HDM from 40 to 98% and the first reactor ΔT (ΔT(R1)) from 49 to 91 °C were associated with a vacuum residue conversion enhancement of 62.0 to 82.7 wt.%. The developed nonlinear regression prediction of conversion from HDM and ΔT(R1) suggests a bigger influence of ΔT(R1) enhancement on conversion augmentation than the HDM increase. The intercriteria analysis evaluation revealed that the higher first reactor ΔT suppresses the sediment formation rate to a greater extent than the higher HDM. During processing Basrah Heavy vacuum residue, a reduction in hydrodeasphaltization (HDAs) from 73.6 to 55.2% and HDM from 88 to 81% was observed. It was confirmed that HDM and HDAs are interrelated. It was found that the attainment of conversion of 80 wt.% and higher during processing Urals and Siberian Light vacuum residues is possible when the HDM is about 90% and LHSV ≤ 0.19 h−1.

Efficient diaphragm-based Fiber Bragg grating vacuum sensor

An efficient diaphragm-based fiber Bragg grating (FBG) vacuum sensor was designed, developed and experimentally demonstrated. The devised sensor was independently interrogated by spectral and intensity demodulation techniques. In spectral demodulation, a linear red-shift was observed in the Bragg spectrum with enhancement in the vacuum level with sensitivity and resolution of 18.5 p.m./mbar and 6.644 mbar, respectively. In intensity demodulation, a chirped fiber Bragg grating (CFBG) was used as an optical filter for the Bragg spectrum of the FBG which linearly varied reflected light intensity from the FBG with enhancement in vacuum level inside the chamber. The intensity demodulation was able to detect the pressure difference in the chamber from 67 mbar to 0.2 μbar with sensitivity and resolution of 1.40 nW/mbar and 6.41 mbar, respectively. The sensor offered 2000 times faster response time than the reference commercial vacuum gauge for intensity demodulations.

Hurdle Approach for Control of Enzymatic Browning and Extension of Shelf Life of Fresh-Cut Leafy Vegetables Using Vacuum Precooling and Modified Atmosphere Packaging: Commercial Application

Fresh-cut leafy vegetable has an image as a healthy, nutritious, and delicious product. However, the product still faces the challenge of quality retention and short shelf life, especially in tropical climate regions. Enzymatic browning in fresh-cut leafy vegetables is considered one of the most important attributes limiting the shelf life of the product. The hurdle approach using commercial vacuum precooling in combination with modified atmosphere packaging (MAP) as an alternative to the use of chemical preservatives to prevent enzymatic browning, an undesirable attribute that is easily detected by consumers, was investigated. The hurdle technology exhibited synergistic effects on fresh-cut lettuce, namely frillice iceberg, romaine, and red oak, in slowing down cut-surface browning, maintaining quality, delaying microbial growth, and extending shelf life of salad products at the retail level. The findings of the study verified the potential of the hurdle approach in delaying the effect of cutting as well as extending shelf life of the product stored at 4 ± 1 °C with 85% RH from three days to nine days with an additional unit cost of 1.05%. Therefore, our hurdle approach is anticipated as the practice with non-chemical and economical approach in the supply chain of the fresh-cut, leafy vegetables industry.

Intercriteria Analysis to Diagnose the Reasons for Increased Fouling in a Commercial Ebullated Bed Vacuum Residue Hydrocracker.

The intercriteria analysis developed on the base of intuitionistic fuzziness and index matrices was applied to evaluate processing data of the LUKOIL Neftohim Burgas H-Oil ebullated bed vacuum residue hydrocracker with the aim of revealing the reasons for increased fouling registered during the 3rd cycle of the H-Oil hydrocracker. It was found that when the ratio of the ΔT of the 1st reactor to the ΔT of the 2nd reactor gets lower than 2.0, an excessive H-Oil equipment fouling occurs. The fouling was also found to be favored by processing of lower Conradson carbon content vacuum residual oils and increased throughput and depressed by increasing the dosage of the HCAT nanodispersed catalyst. The fouling in the atmospheric tower bottom section is facilitated by a lower aromatic content in the atmospheric tower bottom product. The addition of FCC slurry oil not only increases aromatic content but also dissolves some of the asphaltenes in the atmospheric residual hydrocracked oil and decreases its colloidal instability index. The fouling in the vacuum tower bottom section is facilitated by a higher saturate content in the VTB. Surprisingly, it was found that the asphaltene content in the VTB depresses the fouling rate. No relation was found of the sediment content in the hydrocracked residual oils measured by hot filtration tests and by the centrifuge method to the equipment fouling of the H-Oil hydrocracker.

Lightening Impulse Breakdown of Vacuum Gaps in Series—Part II: Bridging Resistor

In part I of this series article, it was found that a negative charge process after a partial breakdown (PB) could reduce the breakdown voltage of vacuum gaps in series. This part proposes the use of a bridging resistor to mitigate this negative charge process and improve the breakdown voltage of the entire arrangement. Two commercial vacuum interrupters (VIs) of the same model were connected in series, with each VI having a grading capacitor connected in parallel. A bridging resistor was then bridged between two floating potential middle points: at the middle point between the VIs and at the middle point between the grading capacitors. Experiments were performed using various gap distance arrangements and resistance values. A noncontact measurement method using an electric field sensor was proposed to measure the floating potentials of the two VIs. Experimental results showed that the negative charge process could be mitigated using the bridging resistor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g}$ </tex-math></inline-formula> by blocking the discharge current from the grading capacitor into the broken-down VI. The voltage distribution between the two VIs became uneven because of the bridging resistor, but the breakdown voltage of the series-connected gaps increased significantly, regardless of the resistance value. The increase rate was influenced by the gap distance arrangement. With a symmetrical gap distance arrangement for the two VIs, a maximum increase rate of 37.4% was reached when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g} =40\,\,\text{k}\Omega $ </tex-math></inline-formula> . With asymmetrical arrangements, when smaller gaps shared higher voltages, the increase rate reached a maximum of 52.8% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g} =70\,\,\text{k}\Omega $ </tex-math></inline-formula> , but it only reached a maximum of 38.9% when larger gaps shared higher voltages with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{g} =10\,\,\text{k}\Omega $ </tex-math></inline-formula> .

Sar-Ad Method to Characterize Vacuum Residues from Different Origins as a Tool to Investigate the Performance of a Commercial Ebullated Bed Vacuum Residue Hydrocracker

Sar-Ad Method to Characterize Vacuum Residues from Different Origins as a Tool to Investigate the Performance of a Commercial Ebullated Bed Vacuum Residue Hydrocracker

Improving Shelf Life, Maintaining Quality, and Delaying Microbial Growth of Broccoli in Supply Chain Using Commercial Vacuum Cooling and Package Icing

Poor and inconsistent quality is a major barrier to increasing produce consumption, and the lack of shelf-life after purchase is the quality issue at retail displays of produce. This research aimed to investigate and identify cooling techniques, namely vacuum cooling and package icing used in supply chains, and any resulting extension of broccoli shelf-life, maintenance of physicochemical quality, and delay in microbial growth at retail stores. Broccoli (Brassica oleracea var. italica cv. Montop) sustainably grown in the highlands of northern Thailand, Chiang Mai Province, under the Royal Project Foundation was experimented on vacuum cooling and package icing were selected to precool broccoli to 4 ± 1 °C. The effects of vacuum cooling using a final pressure of 0.6 kPa for 30 min and package icing using liner Styrofoam boxes (the best ratio of broccoli to crushed ice was 1:1 w/w) on physicochemical qualities, microbial growth, and shelf-life in simulated refrigerated retail displays were examined. The results illustrated that the shelf-life and quality of broccoli could be extended using both vacuum cooling and package icing. Both precooling techniques inhibited the yellowing of florets, provided high sensory scores, delayed microbial growth, and could be able to extend the shelf-life of broccoli. However, package icing offered greater potential for maintaining quality, especially retaining bioactive compounds, and extending shelf-life, thereby increasing the produce market window from 5 to 12 days at 8 ± 1 °C with 85% RH. Therefore, package icing was recommended in the supply chain for fresh broccoli cv. Montop grown in northern Thailand.

Effects of casting parameters and impurity concentrations on as-cast U–10Mo

This work investigates the effects of casting parameter changes on as-cast uranium-10 wt% molybdenum (U–10Mo) alloys on a 1–2 kg scale. A commercial tilt-pour vacuum induction melting system was utilized to study the effects of casting atmosphere, total heating time, hold time at maximum temperature, mold temperature, and crucible type on as-cast U–10Mo impurities and dendrite size. Fourteen plates of differing geometry were cast and analyzed for carbon, oxygen, hydrogen, and nitrogen impurities, as well as molybdenum content. Primary dendrite lengths (PDL) in the microstructure are quantified. A statistical evaluation was performed to identify key carbon and oxygen relationships with operating parameters, impurities, and PDL. Additional factors investigated include crucible material, time at maximum temperature, and total heating time. Zirconia crucibles reduced carbon content on average by 35 % over traditional graphite crucibles. There was statistically relevant associations between carbon and oxygen content, oxygen content and maximum temperature hold time, mold temperature and PDL, and between PDL, maximum temperature hold time, and mold temperature.

3D‐Printed Pneumatically Controlled Soft Suction Cups for Gripping Fragile, Small, and Rough Objects

A 3D‐printed pneumatically actuated soft suction gripper with an elastomer film is proposed. Suction in such gripper is actively controlled by applying a negative pressure behind the film. The elastomeric gripper body is 3D‐printed, making it easy to customize and integrate into future robotic gripping systems. The gripper can pick a wide variety of objects, such as delicate fruits, small parts, and parts with uneven loads, with high pull‐off forces (over 7.4 N with ∅ 20 mm/55 kPa). The achieved pull‐off forces are significantly higher than the previously reported suction cup grippers with films and more comparable with commercial vacuum grippers. The pull‐off forces show no significant differences with surfaces of varying roughness (up to root‐mean‐square roughness of 5.66 μm) and the gripper is able to pick and release target objects repeatedly. The gripper is also compared with a commercial vacuum gripper with comparable dimensions. It outperforms the commercial gripper in the case of fragile objects, objects smaller than the gripper diameter, and objects with uneven loads. It can apply high pull‐off forces while having controllable release, and is suitable for gripping a wide variety of real‐world objects, including heavy, rough, small, thin, and fragile ones.

Atomic precision imaging with an on-chip scanning tunneling microscope integrated into a commercial ultrahigh vacuum STM system

In this article, we replace the Z axis of the piezotube of a conventional Ultrahigh-Vacuum (UHV) Scanning Tunneling Microscope (STM) with a one-degree-of-freedom Microelectromechanical-System (MEMS) nanopositioner. As a result, a hybrid system is realized in which motions in the XY plane are carried out by the piezotube, while the MEMS device performs the Z-axis positioning with a smaller footprint and higher sensitivity. With the proposed system and a feedback loop, STM imaging is conducted on an H-passivated Si (100)-2×1 sample in a UHV condition, demonstrating that this on-chip STM is conducive to atomic precision scanning tunneling microscopy.

Open Source Vacuum Oven Design for Low-Temperature Drying: Performance Evaluation for Recycled PET and Biomass

Vacuum drying can dehydrate materials further than dry heat methods, while protecting sensitive materials from thermal degradation. Many industries have shifted to vacuum drying as cost- or time-saving measures. Small-scale vacuum drying, however, has been limited by the high costs of specialty scientific tools. To make vacuum drying more accessible, this study provides design and performance information for a small-scale open source vacuum oven, which can be fabricated from off-the-shelf and 3-D printed components. The oven is tested for drying speed and effectiveness on both waste plastic polyethylene terephthalate (PET) and a consortium of bacteria developed for bioprocessing of terephthalate wastes to assist in distributed recycling of PET for both additive manufacturing as well as potential food. Both materials can be damaged when exposed to high temperatures, making vacuum drying a desirable solution. The results showed that the open source vacuum oven was effective at drying both plastic and biomaterials, drying at a higher rate than a hot-air dryer for small samples or for low volumes of water. The system can be constructed for less than 20% of commercial vacuum dryer costs for several laboratory-scale applications, including dehydration of bio-organisms, drying plastic for distributed recycling and additive manufacturing, and chemical processing.

Application of artificial neural networks for predicting parameters of commercial vacuum cooling process of baby cos lettuce

AbstractArtificial neural networks (ANNs) demonstrated sensitive results in predicting final temperature and weight loss percentage of commercial vacuum cooling process. According to the results for final temperature, ANNs showed better prediction performance than multiple linear regression in all criteria, including an adjusted R‐squared (R2adj) of .932 and root mean square error (RMSE) of 0.579. In addition, the predicted values of weight loss percentage from ANN models were in good agreement with all experimental data (Radj2 = .82 and RMSE = 0.286). The process parameters from proper ANN model was subsequently used to investigate the effect of vacuum cooling on the qualities of baby cos lettuce during storage compared with the non‐precooled samples. The results suggested that vacuum cooling was an effective method for extending shelf life of baby cos lettuce from 9 to 16 days at 4°C. Qualities of fresh lettuce vacuum cooled using selected process parameters simulated from proper ANN model were significantly better than the non‐precooled sample during storage (p ≤ .05).Practical ApplicationsVacuum cooling widely considered the best precooling technique for horticultural produce. However, vacuum cooling also has some disadvantages including weight loss and freezing injury occurring during the vacuum cooling process, due to the setting of inapplicable parameters before the vacuum cooling process such as final pressure and holding time. Experimental study of the optimum vacuum cooling parameters for baby cos lettuce in each season (winter or summer) takes a long time and is expensive. Therefore, the present study emphasized the effects of vacuum cooling parameters setting on final temperature and weight loss percentage of baby cos lettuce. Prediction methods using artificial neural network (ANN) allow for vacuum cooling processes based on experimental research to be recommended as feasible at an industrial scale.

Study of the influences of different factors on the charged particles absorbed by the post-arc anode during the post-arc sheath expansion process in vacuum circuit breakers

The dielectric recovery process has decisive effects on the current interruption process in vacuum circuit breakers, which has attracted the special attention of researchers. In commercial vacuum interrupters, ions and electrons of the residual plasma between the contact gap are separated and then fly to the electrodes under the effect of the transient recovery voltage after current zero. During this period, the post-arc current forms. During the formation of the post-arc current, ions also enter the post-arc anode due to their thermal motion. Therefore, the number of net electrons, which form the post-arc current, is only part of the total electrons between the contact gap at current zero. During the post-arc sheath expansion process, almost all electrons in the contact gap will enter the post-arc anode under the effects of the transient recovery voltage. If the proportion of ions and electrons, which enter the post-arc anode, can be obtained, the total number of electrons and consequently the residual plasma density between the contact gap could be estimated from the integration of the post-arc current. In this paper, the influences on the absorption of charged particles by the post-arc anode of some factors, e.g., rising rate of transient recovery voltage and metal vapor, have been simulated and discussed with a one-dimensional particle in cell-Monte Carlo collision model.

Experimental study on field emission current in vacuum interrupter at functional limit of vacuum pressure

Significant number of medium voltage Vacuum Interrupters (VI) are currently operating at their lifetime limit of 20–30 years and beyond. Estimation of the pressure inside the VI and of the contact surface condition without demounting of the VI are of importance for Vacuum Circuit Breakers (VCB) operating at medium voltage range and for further development of the VI technology towards higher voltages. This paper reports on the measurements of the field emission current in a commercial vacuum interrupter 12 kV/2500 A/40 kA with the pressure controlled at the VI functional limit of 0.04 Pa. The Fowler-Nordheim equation was applied to indicate the vacuum pressure within the functional limit and to evaluate the influence of the contact surface condition on the microscopic surface projections. A relation between the microscopic processes and the field emission current was studied. The measurement results are presented for a small fixed contact gap of 0.3 mm allowing relatively low DC test voltage level up to 40 kV.

An investigation of the survival and/or growth of Clostridioides (Clostridium) difficile in beef stored under aerobic, anaerobic and commercial vacuum packaging conditions at 2 °C and 20 °C

Although primarily considered to be a nosocomial infection, there is mounting evidence that food, including beef products, may be a source of Clostridioides (Clostridium) difficile. The objective of this study was to investigate the behaviour of this pathogen under atmospheric and temperature conditions that may be encountered in vacuum packaged retail beef. Inoculated steaks were stored in air, in low (950 cm3/m2·d· bar), medium (<47 cm3/m2·d· bar) and high barrier (<3 cm3/m2·d· bar) vacuum packs and under anaerobic conditions at 2 °C and 20 °C. At 2 °C a steady decline in C. difficile concentrations was observed over the 32 days of storage, regardless of oxygen conditions. In contrast, in the temperature abuse scenario, the bacterial counts were significantly (P < 0.05) higher in the medium and high barrier packs and under anaerobic conditions after 2 days and increased up to approximately 5 log10 cfu/g by day 8. It was concluded that under chilled conditions, C. difficile will survive, all-be-it at lower concentrations, for extended periods (up to 32 days) but in a temperature abuse scenario these bacteria will grow on beef steaks stored in medium and high barrier vacuum packs and under anaerobic conditions. Given the increase in community acquired C. difficile infections, the potential role of vacuum packaged steaks as a foodborne source of these pathogens requires further investigation.