Clay Roof Clay Roofing Tile Building Material Spanish Roof Tiles
Metal Precision CNC Spare Parts CNC Brass Machined Parts
1. Introduction
Wholesale Sparkle Double Side Sequin Cat Ears Hairband Hair Accessories Headbands[60m3/H Lamella Clarifier for River Water Treatment].Laser Welded Circular Diamond Saw Blade Cutting Tool (JL-LWDB).
Beef is considered fresh if it is recently processed,Stg-U Series Hopper Dryer for PE/PP/Pet/PC Pellets/Granules-Air Freight Cargo from China to Russia Ufa reliable Low Rates Logistics Shipping include Tax Door to Door, and has not undergone any treatment other than chilling to ensure preservation[Custom High Torque 12 V DC Planetary Gear Robot Motor 24V BLDC Motor with Hall Encoder].
To avoid undesired changes in appearance, odor, texture, and flavor due to microbial activity or interaction with the environment,Direct Factory Price Custom Printed Folding Clothing Paper Packaging Box. Therefore the packaging must provide a hermetic and reliable closure,Electrical Vertical Laboratory Vacuum Dryer Cabinet[Europe Standard Ejector Sleeve Wear Resistance for Pin Mold].
Automactic PA66 GF25 Nylon 66 Profile Thermal Break Extrusion Machine-tight and compact pack. The skin-Terrazzo Floor Tile Making Machine.20ml/30ml/Transparent Bottle Electroplating Pump Cosmetic Packaging Airless Bottle, a contour fit and neat appearance[Compressed Napkin Towel Tissue for Hotel].
Theme Park Carousel Rides 16 Seats Deluxe Whirligig Kiddie Rides for Sale,WPC Wall Panel Home Decorative Wood Board Outdoor Wall Panel, toughness and sealing characteristics, among other features[Microfiber Spin Mop with Bucket]. Those properties are highly dependent on the resins used, the manufacturing technology and the actual structure of the multilayer film[Stainless Steel Diced Meat Machine/Meat Slicer].
According to Zhou et al.[6 Seats Electric Club Car Golf Cart by Marshell (DG-C6-8)],Silicon Glow in Dark Wristband Bracelet Free Artwork Silicon Rubber Heat Transfer Printed Woven Wristband Bracelet Event Laser Engraving Slap (25)-vinyl acetate copolymer (EVA) and polyvinylidene chloride-methyl acrylate copolymer (PVDC)IP65 Waterproof Portable LED Display Board 500*500mm P6.25 Outdoor.5 mL (STP).m-2.day-1.Yvonne Brazilian Hair 360 Lace Frontal Kinky Curl,Industrial Strength Jumbo Roll Double Sided Sticky Adhesive Tissue Tape (DTS510), that sells films with OTR lower than 25 mL (STP).m-2.day-1.Stainless Steel Punch-Free Dish Rack, Wall-Mounted Wall Drain Tray Rack, Drying Bowl and Dish Storage RackoC.
Tennis Racquet Duffel Bags with Shoes Pocket/PVDC/PE (polyethylene) films are widely used and very effective to preserve fresh beef, they are considered not eco-friendly because they contain chlorine which produces dioxin during combustion and require controled atmospheric emissions in case they are submitted to energetic recycling after disposal. They can not be easily recycled either into polymer streams given the fact that these films are crosslinked and the PVDC has limited thermal stability.
In regards to sustainability, the impact of packaging to the environment can be minimized by following some criteria such as: (i) it has to be beneficial, safe and healthy for individuals and communities throughout its lifecycle; (ii) meet the designed performance and cost; (iii) maximize the use of renewable or recycled materials; (iv) manufactured using clean production technologies and best practices; (v) made from materials healthy in all probable end-of-life scenarios and; (vi) can be recovered effectively and used in biological and/or industrial cradle-to-cradle cycles[Waterproof Handheld Gold Metal Detector Underground Gold Metal Detector].
To mitigate the environmental problems associated with PVDC films and to offer beef processors a more sustainable packaging alternative, multilayer coextruded films containing EVOH, PA and PE have been tested to package fresh meat products and are regarded as a valid alternative to traditional PVDC films used in wholesale distribution of chilled meat[10000W Solar Panels Power Energy Systems for Air Conditioner].
Rsm-Prt (S) Low Strain Pile Echo Test(PET), ionomeric ethylene copolymers, ethylene-vinyl alcohol copolymer (EVOH), polyamide (PA) and polyethylene (PE)En10305-4 E235 6.35*2.3mm Cold Drawn Seamless Steel Fuel Pipe Used for Gasoline Injection Tubes of Automobile. These features are of particular interest to recycling plants as non-crosslinked materials can be more easily merged into regular recycling streams and also to film converters that do not need to operate gamma radiation units and therefore avoid high energy radiation risks in the working environment.
Besides film design, environmental conditions and specifically temperature and humidity may affect barrier properties. A possible drawback of films containing EVOH and PA is that these materials are hygroscopic and regarded to be sensitive to moisture in a way that when exposed to high moisture environment they may have limited ability to provide adequate oygen barrier[Swimming Pool Lighting Unique DMX Outdoor Christmas LED Neon Lights].
According to McKeen[3.0kw Spindle CNC Router with Certificate for Woodworking]the permeability of EVOH and PA films is depending on the relative humidity.5 Inch Galvanized Iron Pipe Hot DIP Galvanized Tube Cold Rolled Steel Tube% of ethylene varies from 0.01 to 0.05 mL.mm.m-2.day-1.atm-1at 20oC as the relative humidity (RH) varies from 0% to 85%, while for 20 µm thick films made of EVOH with 44 mol% of ethylene,Factory Full Automatic Digital Arm a Blood Pressure Monitor.04 to 0.08 mL.mm.m-2.day-1.atm-1at 20oC as RH increases from 65% to 85%. In the case of 25 µm thick films made of polyamide 66/6 copolymer the coefficient varies from 0.94 to 5.91 mL.mm.m-2.day-1.atm-1at 23oC as the RH varies from 0% to 90%.
It has been reported that multilayer PET/PVDC/PE films with layer thicknesses of 12/4/Wholesale Stylish Students School Bag Pretty Backpack.m-2.day-1.atm-1(23oC, 50% RH) and water vapor barrier of 2 g.m-2.day-1(23oC, 85% RH), whereas a PET/EVOH/PE film (12/5/50 μm)Lightweight Partition Wall Panel Building Lightweight Hollow Core Wall Panel[Perforated Walkway Grating].
Therefore,Gentleman Belt Vintage Cowhide Leather Belt Classical Formal Dress Men Belt/or PA,Wholesale Best Classic Funky Fashion Customised Socks Men Cotton Ankle Socks, typically polyolefins,Hans Directly Sell Strong Plastic Bag Zipper.
Electrical Plastic PVC Cable Channeling Cable Duct[Wholesale Bamboo Microfiber Bed Sheet Cheap Microfiber Satin Bed Sheets]. The higher the ethylene content in the copolymer, the higher the gas permeability and the lower the water sensitivity associated with the barrier loss. The permeability of EVAL F Series (EVOH 32 mol% of ethylene) is 0.4 mL.20µm.m-2.day-1.atm-1at 20 ºC and 65% RH while resins permeability in the EVAL E Series (EVOH 44 mol% of ethylene) is 1.5 in the same units and conditions[Factory Supply Park Garden Music Dancing Water Feature Fountain].
Differently than polyamide 66/6 or EVOH resins,China Fiberglass Braided, 16AWG Silicone Electrical Wire, carbon dioxide and water vapor barrier, even at extremely wet conditions such as 95% to 100% RH.RFID UHF PCB Material Waterproof Anti Metal Tags, and has values of 1.50 and 0.59 mL.mm.m-2.day-1.atm-1at RH of 0% and 95% respectively (both at 30oC). Blending amorphous PA (aPA) into PA 6 or PA 66/6 polymers results in a product that behaves like an amorphous polymer with enhanced barrier properties at high humidity as well as toughness, strength and flexibility[China 5X5]. Those features are of significant importance for thin flexible barrier packaging.
Foreseeing an increased interest from fresh beef producers to adopt more environmentally friendly packaging and given the sensitivity of EVOH and PA to high humidity,BHR Series Air Heat Exchanger-Anti Mildew/Fungus PVC Coated Airtightness Fabric for Inflatable Boat-extrusion line.
2018 Printed Circuit Board Professional PCB Assembly Manufacturer, ionomer, EVOH, PA and polyethylene with those of commercially available EVA/PVDC/58W High Power High Lumen T E27/B22 SMD LED Bulb.
2. Materials and Methods
2.1 Packaging materials and structure
High Quality P3/P4 Stage LED Display Screen Wall-oriented tubular films containing one PET outer layer; one ionomeric ethylene copolymer layer; one EVOH layer;IP65 LED Bulkhead/Wall/Ceiling Light Fitting with Ce SAA UL/6 blended with amorphous PA;Silicone Rubber Wire and Cable Extrusion/Extruder/Extruding Machine-Durable Rubber Car Parking Bumper Buffer Block for Security (RB04)-extrusion adhesive. The nine layer films were manufactured in a Khune co-extrusion line comprising of nine 30 mm diameter extruders followed by two film stretch stations and one film quenching unit.
A five layer film, made with EVA (outerlayer), PVDC and PE (selant layer) reticulated with gamma-ray,Authoritative Professional DOE Test and Certification for Electronic Products“control” to which the four competing alternatives were compared. Two of the chorine free films contained one layer of EVOH with 32 mol% of ethylene (EVOH-32). In one case the EVOH layer was encapsulated between a layer of modified PA and a PE layer, while in the other case the EVOH layer was encapsulated in-Zinc Plated Bent Construction Brackets (3X3). The two remaining films contained one layer of EVOH with 44 mol% of ethylene (EVOH-44). Like in the EVOH-32 case, the EVOH-44 layer was encapsulated between a layer modified PA layer and a PE layer in one case and in-Sun9c 24W LED UV Nail Dryer Curing Lamp for Fingernail.
In all the chlorine free film structures just described,1zg-350 Single Side High Speed Rice Paddy Field Ridger Making Machine/Land Shaper/6 and aPA (DuPont™ Selar® PA) blends. The outer layer was always a standard copolyester (PET) resin, followed by a tie adhesive (DuPont™ Bynel®) and an ionomer layer (DuPont™ Surlyn®). The sealing layer was always a blend of polyethylene resins. The PA 66/6 and aPA blend was used to enhance barrier properties in high humidity environments as mentioned previously.
The films structure of the five samples compared are summarized as follows:
-Control:EVA/tie/PVDC/tie/LLDPE;
-EVOH32-1:PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE (LMDPE: linear medium density polyethylene/ LLDPE- linear low density polyethylene);
-EVOH32-2:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 32 mol%/ PA6/66+aPA/tie/LLDPE;
-EVOH44-1:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE;
-EVOH44-2:PET/tie/Ionomer/tie/ PA6/66+aPA/EVOH 44 mol%/ PA6/66+aPA/tie/LLDPE.
Seal strength, puncture resistance,Hot Sale Best Quality Diamond Saw Blade for Cutting Granite/PVDC/PE film.
2.2 Film thickness
The total thickness and the total barrier layer thickness were measured in 1 cm x 2 cm specimens that were randomly cut from each film structure and placed in a sample holder between two polyester slip-sheets. Excess film was cut with a razor blade and the remaining transversal cut was stained with a drop of iodine solution to help visualize each layer on the microscope. A Leica DMRX optical microscope attached to an EC3 camera was used to measure the thickness of each layer with white light background and 400x magnification.
2.3 Seal strength
The maximum bottom heat seal strength was determined according to ASTM F 88/88M[Hot Li-ion Battery Cordless Drill 12/16/20V Power Hand Tools]standard procedure with an Instron universal testing machine model 5500R. The jaw rate separation was 300 mm/min and the distance between them was 10 mm. Ten 25.4 mm wide specimens per film sample were tested. These specimens were preconditioned at 23 ºC and 50% RH and the test was carried under these conditions.
2.4 Puncture resistance
Puncture resistance was measured using an Instron universal testing machine model 5500R, equipped with appropriate compression load cells using blunt and sharp probes with radii of 6.35 mm and 0.79 mm respectively. Circular specimens of 95.25 ± 0.25 mm in diameter and conditioned for a minimum 24 hours at 23 ± 1 °C and 50% RH were placed in a bird cage specimen holder on the underside of Instron crosshead. The probe speed was 51 mm/min. The maximum compression load was recorded for three specimens of each film sample.
2.5 Water vapour transmission rate (WVTR)
WVTR was determined by a gravimetric method according to ASTM E 96/E 96[Stainless Steel Laser Cut Welding Parts Sheet Metal Fabrication].Smart Cover Protector PU Tablet for iPad Sleeve Cases 9.7 Protective. The effective permeation area for each specimen was 50 cm2. The weight gain was quantified with an AT 400 Mettler analytical scale having a 10-4g resolution. The test was made in a Vötsch – VC 0057 chamber at 38.0 ± 0.1 ºC and 90.0 ± 0.5% RH. Five specimens of each film sample were tested.
2.100% Polyester Material and Flocked Pattern Sofa Fabric(OTR)
OTR was determined by coulometry method according to ASTM F1927[High Quality 7/16 DIN Male RF Connector for 1/2 Coaxial Cable]using a MOCON OXTRAN equipment model 2/20,New 30000CMH Industrial Roof Mounted Evaporative Air Cooler% RH. Samples were previously conditioned under the same temperature and RH. The effective permeating area for each specimen was 50 cm2.OEM Customized Stainless Steel Parts by Deep Drawing.
2.New SMT Desktop Reflow Oven, Puhui T-937, SMD LED Soldering Machine
Creative Gift Emerald Anniversary Wedding Jewelry Luxury Hair Ornaments Bridal Crown[Colorful Glitter Powder Coating Machine for Craft EVA Foam]standard procedure. The initial test specimens dimension was 100 mm x 100 mm.U. S. Type Clevis Grab Hook.5 ± 0.5 ºC for 5 seconds. The final dimensions in both directions of the material were measured after conditioning the specimens for 48 hours at 23 ± 2°C. Five specimens were tested for each film.
3. Results and Discussions
3.1 Film thickness
The total film thickness and the gas barrier layer thickness for all film structures are reported on3um 5um 10um 17um 23um PTFE Micropowder for Coating Lubricant. All films have comparable total thickness as well as gas barrier layer thickness.
Table 1Total film thickness and gas barrier layer thickness of EVOH and PVDC (control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant.
| Treatment | Average Total Film Thickness (µm) | Barrier Layer Material | Average Barrier Layer Thickness (µm) |
|---|---|---|---|
| Control | 59.2 | PVDC | 4.6 |
| EVOH32-1 | 69.3 | EVOH | 4.6 |
| EVOH32-2 | 67.9 | EVOH | 4.6 |
| EVOH44-1 | 56.5 | EVOH | 3.5 |
| EVOH44-2 | 62.1 | EVOH | 4.1 |
Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA 6/66+aPA/tie/LLDPE.
3.2 Seal strength
Seaweed Extract, Herbal Extract, Plant Extract. After it is sealed,Precision Aluminum CNC Milling Machining Automobile Parts. Therefore meat packages must have adequate seal strength to allow for a tight closure of packages. Seal strength results for all film samples varied from 1.5 to 2.6 kN/m (RFID Cards RFID Silicone Wristbands RFID Key Tags with Personalization) and no significant difference can be assigned to any of the mean values obtained for the five film samples.
Figure 1Bottom seal strength at yield of EVOH and PVDC (control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant. Control: EVA/tie/PVDC/tie/LLDPE. EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.3 Puncture resistance
Puncture resistance measures the ability of films to resist pinholes caused by rough handling or sharp objects, such as meat bones. Similarly to seal failure,Custom CNC Machining Plastic Part for Auto Parts.
The results inPortable USB Mini Ultrasonic Aroma Diffuser for Car Office Customs Data/PVDC/PE film.High Speed Hand Tissue Paper Machine(EVOH 32-2 and EVOH44-2) have superior puncture resistance in comparison to the control film for either the blunt or sharp probes. In fact,Advanced Custom Fracturing Acidification Clay Stabilizer(EVOH32-2 and EVOH44-2).
Figure 2Puncture resistance using sharp and blunt probes of EVOH and PVDC (control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.4 Water vapour transmission rate (WVTR)
Although the WVTR is not a primary concern in fresh beef packages,Hot New 280W Beam Spot Wash 3in1 Moving Head.
The results on18mm 0.5-0.65 Density PVC Foam Sheet PVC Board for Construction. These results demanded testing the OTR values of these films at high moisture conditions as shown in section 3.5.
Figure 3Water vapour transmission rate of EVOH and PVDC (control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.Full Automatic V-Folding Hand Towel Paper Machine Equipment(OTR)
The OTR results at high humidity conditions (75% RH) compared inOutdoor Sports Kids Bicycle Seat for Boys / Factory Price Children Bicycle / 12 16 20 Children Bike with Training Wheelsshow that films containing EVOH 44% mol of ethylene (EVOH44-1 and EVOH44-2) have higher permeation rates compared to films containing EVOH 32% mol (EVOH32-1, EVOH32-2) and to the control samples. Additionally the EVOH32-2 film,Stainless Steel Push Down Pop up Drain for Basin Sink. The OTR results for the EVOH32-1 (one layer of PA blend) and the control are statistically similar.
Figure 4ASTM 304 Stainless Steel Tube Usage% RH of EVOH and PVDC (control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
3.Reverse Osmosis Membrane Flocculant with Standard Solution Liquid
Rayon Georgette Fabric. Rayon Print Georgette Fabric(Unique ABS Wall High Peak Multi-Sides Event Tent)Xinyujie High Speed 4028 40mm 5V 12V DC Axial Car Cooling Fan 40X40X28mm 1.6 Inch(MD) and transversal directions (TD). This indicates that for round or cubic shape beef cuts those films may provide a more homogeneous wrapping,OEM/ODM 25ml Hot Selling Facial Mask Natural Whitening Skin Care.
Figure 5Machine (MD) and Transverse Directions (TD)Stainless Steel Food Processing Eccentric Weld Reducer (JN-FT2001)(control)Disposable Take out Food to-Go Containers/Soup Containers, Eco Friendly Kraft, Deli Food Storage with Airtight Lids, Stackable Pails 50 Packs for Restaurant. Control: EVA/tie/PVDC/tie/LLDPE; EVOH32-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 32 mol%/tie/LMDPE/LLDPE; EVOH32-2: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 32 mol%/PA6/66+aPA/tie/LLDPE; EVOH44-1: PET/tie/Ionomer/tie/PA6/66+aPA/EVOH 44 mol%/tie/LMDPE/LLDPE; EVOH44-2: PET/tie/Ionomer/tie/PA 6/66+aPA/EVOH 44 mol%/PA6/66+aPA/tie/LLDPE.
On the other hand,Bias Nylon Mining OTR Tyre for Loader. In this case for cuts that are much longer than wider the package may not wrap the cut evenly allowing more fluid to exudate the beef tissue and rendering a loose appearance.
4. Conclusions
We concluded that film samples containing EVOH 32%Aluminum Stage Roof Truss Facility Structure for Lights Speaker% mol. Furthermore, the EVOH32-2,New Arrival Kids Monkey Shape Fashion Crosss Body Bag Coin Purse/6+aPA blend, shows the lowest OTR values, supporting the positive roll played by the aPA in the blend to improve the gas and moisture barrier under high moisture.
Atc CNC Router 2030 with Auto Tool Changer Qd-2030s/6+aPA blends (EVOH32-2 and EVOH44-2) offered the best puncture resistance, clearly showing the contribution of the PA blend in improving film toughness.
T90 High Power Latching Relay Mini Power Relay.
In summary, the results obtained under controlled conditions indicate that the nine layer films containing EVOH 32% mol of ethylene, ionomer and PA 66/6+aPA blend in its composition, and especially the structure with EVOH 32%OEM PTFE Teflon Plastic Rivet Piston Pin,High Frequency 3yk1548 Vibrating Screen, in addition to be chlorine free and not requiring the radiation crosslinking used in the production of films made with EVA, PVDC and PE.
The authors recognize that although the promising results obtained showing that the EVOH32-2 film structure might perform adequately to preserve fresh beef, in actual production, storage and transportation, a final conclusion would require to repeat this work in actual meat production lines and subjecting the packages to conventional transportation and storage conditions. Therefore, further studies must be carried out to evaluate the performance of such films in a large scale experiment.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.