Podajalnik S Trenjem nakup rabljenega (85.237)

Stanje: dober (rabljeno), Tehnični podatki o paletnem regalnem stojalu: Regalni sistem: Dexion Tip: S 4 V obsegu dobave je vključeno: 01x paletno regalno stojalo, rabljeno Barva materiala: sendzimir pocinkano Tip: H Dimenzije profila: 81,7 x 77,21 x 2,5 mm Vključno s prečnimi in diagonalnimi povezavami, Talne plošče Stojala so predmontirana (vijačen okvir) Višina: 11.050 mm Globina: 1.100 mm Vaše kontaktne osebe pri nas: Gospod: Andre Evering Gospod: Mario Klöver Gospod: Falk Deutsch Dodjxxq Tvjpfx Aflswa Splošne informacije o artiklu: Ta artikel je na voljo samo za osebni prevzem. Za morebitno dodatno transport ali pošiljanje tega artikla nastanejo dodatni stroški, ki jih je možno individualno preveriti glede na kraj dostave in obseg dobave.

Stanje: dober (rabljeno), Profesionalni trifazni električni motor priznane nemške družbe KAISER – Elektromotoren-Werke Kaiser. Masivna industrijska zasnova, namenjena neprekinjenemu delovanju v industrijskih strojih, črpalkah, ventilatorjih, obdelovalnih strojih, kompresorjih in tehnoloških pogonih. Motor ima prirubni nosilec in gred s premerom približno 28 mm z utorom za pero. Tehnični podatki: • Proizvajalec: Elektromotoren-Werke Kaiser • Tip: DN 112 S/2 • Moč: 4,0 kW • Napajanje: 380V • Tok: 9,0 A • Frekvenca: 50 Hz • Obrati: 2880 obr/min • Trifazni motor • Premer gredi: cca 28 mm • Prirubno pritrditev • Masivno industrijsko ohišje • Izdelano v Nemčiji Uporaba: • črpalke, • ventilatorji, • industrijski stroji, • obdelovalni stroji, • kompresorji, • tehnološki pogoni, • proizvodne naprave. Stanje: Rabljeno blago. Kaže običajne znake uporabe in skladiščenja. Dejanski videz viden na fotografijah. Dwodsy Nm Tvspfx Aflja

Stanje: dober (rabljeno), Jones & Lamson Progres Industriel Lathe Type: Senna 1H Swing over bed: 520 mm Maximum swing over bed: 780 mm Swing over cross slide: 380 mm Turning length: 3500 mm Spindle bore: 70 mm Dedpfsncc H Hox Afljwa Spindle speed: 1800 rpm Diameter of 3-jaw chuck: 315 mm Diameter of 4-jaw chuck: 310 and 440 mm Includes accessories, documentation, and coolant pump Dimensions: 525x115x134 cm (LxWxH)

Stanje: potreben popravila (rabljeno), Leto izdelave: 2007, Color sorter Separation & Sorting Technology GmbH Year 2007 Sensors are missing Catalogue available Dwsdpeu Icgbjfx Aflja

Stanje: novo, Working width 3500 mm Working height 2300 mm Number of pressing cylinders: 4 pcs. S&S electrohydraulic frame press machine, Type Super Options: Working widths from 3,000 mm to 5,000 mm Working heights from 2,000 mm to 3,000 mm Optional equipment with center pressure beam, slanted window device, counter profiles for single-part production, and much more! Request the complete price list from us! Description: With automatic adjustment for corner joints (tenon and mortise joint, other types of corner joints optional), CE compliant version The only self-adjusting high-performance fully automatic frame press where wooden workpieces do not need to be pre-placed. Width and height adjustment takes place automatically, without any loss of time, immediately after the workpieces are directly placed into the pressing area. No repositioning of the timber is necessary. Base machine with heavy-duty welded frame construction, made of oversized, thick-walled special profiles. Guiding rails of the press corners on the pressure beams in wear-resistant, machined design. Continuous stop side support for width pressing, torsion-resistant, mounted on the base frame. Continuous lower support in extremely heavy-duty, torsion-resistant design, connected with base frame and machine feed. Inserting height 500 mm. All stops are finely adjustable for absolute angular precision and long-term accuracy. Sliding carriage on right side with fast motorized width adjustment with guaranteed parallel movement, including automatic hydraulic locking: Central drive for size adjustment horizontally and vertically, with high infeed and adjustment speed and automatic width and height adjustment (opto-electronic). 2 vertical double-acting pressure cylinders, piston diameter 50 mm, 250 mm cylinder stroke, adjustable pressing force from 400 to 2000 kg. 2 horizontal double-acting pressure cylinders, piston diameter 40 mm, 80 mm cylinder stroke, adjustable pressing force from 250 to 1250 kg. Press corners at upper right, in heavy, milled design, with automatic corner adjustment. Removable press corners Contact surfaces with adhesive-repellent finish. Support and pressure plate depth 100 mm. 8-fold hold and positioning device for absolutely loose placement of all frame parts in the pressing area (no pre-assembly required). Each frame part is held and positioned in two places. Automatic lifting function enables ergonomic placement of the upper cross piece for tall frames at an operator-friendly height. Enhanced work safety due to floor-level operation without ladders or steps. All individual frame components are placed directly in the pressing area. Dedpfxed Rzc Rs Aflowa Program selection options: - Manual motorized via push button - Fully automatic via opto-electronic size setting including automatic pressing cycle combined with safety light barrier Automatic, cycle-controlled pressing process via impulse: Vertical pressing – release – horizontal pressing – release – vertical/horizontal pressing Control cabinet is service-friendly, mounted on the left of the base frame. Fast opto-electronic size setting. Compact hydraulic unit adjustable from 20 to 100 bar. Electric hand control, freely programmable for efficient work, especially with large and complex frame structures.

Stanje: novo, številka stroja/vozila: S-CL-100-FN-EC, Funkcionalnost: popolnoma funkcionalen, vhodna napetost: 230 V, volumenski pretok: 134 m³/h, skupna višina: 475 mm, skupna dolžina: 250 mm, skupna širina: 250 mm, skupna masa: 17 kg, Oprema: Na voljo je tipska ploščica, ISI S-CLEANER Mechanical Air Filtration Unit (Solder Fume Extraction) For up to 1 workstation Type: 100 FN Design: Semi-mobile (glide skids / no castors) Control: none Horizontally oriented, semi-mobile mechanical air purifier with EC radial fan for extracting soldering fumes. TECHNICAL SPECIFICATION: Airflow: - 134 m³/h (air volume) - 100 m³/h (effective air output) (depending on filter configuration, without extraction elements) Inlet connection: NW 50 mm (rear) Filter configuration: - Pre-filter - HEPA filter H13 - Activated carbon cassette (refillable) Colour: RAL 7035 light grey Voltage: 230 V Frequency: 50 Hz Protection class: IP54 Fan technology: energy-efficient EC technology Airflow: not adjustable Dwodpfxewpu Tws Aflsa Dimensions: Length 250 mm / Width 250 mm / Height 475 mm Weight: 16.5 kg

Stanje: novo, številka stroja/vozila: S-CL-250-FN-EC, Funkcionalnost: popolnoma funkcionalen, vhodna napetost: 230 V, volumenski pretok: 250 m³/h, skupna višina: 600 mm, skupna dolžina: 340 mm, skupna širina: 430 mm, skupna masa: 35 kg, Oprema: Na voljo je tipska ploščica, ISI S-CLEANER Mechanical Air Filtration Unit (Solder Fume) for up to 2 workstations Type: 250 FN Version: Mobile Control: none Dwedsvrylfspfx Aflea Horizontal, mobile mechanical air purifier with EC radial fan for the filtration of solder fume. TECHNICAL DESCRIPTION: Airflow: - 240 m³/h (nominal airflow) - 170 m³/h (effective air output) (depends on filter configuration, without extraction hoods) Suction ports: 2 x NW 50 mm (rear) Filter configuration: - Prefilter G4 - HEPA filter H13 - Activated carbon cassette (2.5 kg, refillable) Colour: RAL 7035 light grey (custom colour on request) Voltage: 230 V Frequency: 50 Hz Protection class: IP54 Fan technology: energy-saving EC technology Airflow output: not adjustable Dimensions: Length 340 mm / Width 430 mm / Height 600 mm Weight: 35 kg

Stanje: skoraj kot novo (rabljeno), Leto izdelave: 2017, S&F Vibrating Screen Machine | Screening Machine Type ASM-200 used (inspected) with inspected bearings (flange bearings) and inspected universal joints Dwjdpfx Asy Aa Ugeflea Manufacturer: S&F GmbH Type: ASM-200 Year of manufacture: 2017 Screening capacity: approx. 20 t/h (for wood pellets, depending on material) Fractions: 2 Screen area: 2.0 m² per mesh size Screen decks: 1 piece Mesh aperture size: - 1st screen deck: punched perforated plate, D = 5 mm Drive power: 2.2 kW, 3 x 400 V, 50 Hz L x W x H: 3,200 x 1,800 x 1,450 mm Design: ECO Line Machine weight: approx. 1,300 kg Machine color: RAL 3000 Flame Red including: Modular Silo Type M-300 / 45°, used L x W = 3,000 x 3,000 mm Total height: approx. 4,400 mm Outlet height: approx. 1,750 mm Volume: approx. 4.06 or 9.35 m³ Max. bulk density: approx. 900 kg/m³ Article No.: 406.4345 including extension feet L = 1,100 mm including hopper extension and slide gate Suitable for screening the following bulk materials, among others: - Wood chips - Sawdust and wood shavings - Biomass - Wood pellets - Charcoal - Waste wood - Bark vibrating screen | wood chip screen | vibrating screening machine | flat screen | oscillating screen | drum screen | screening machine for wood chips | CHP screening machine

Stanje: novo, Working width: 3,500 mm Working height: 2,300 mm Number of pressure cylinders: 4 pcs. S&S Frame Press Type RP 2000 – CE version Options: Working widths from 3,000 mm to 5,000 mm Working heights from 2,000 mm to 3,000 mm Optional equipment includes central pressure beam, angled window device, counter profiles for single-part production, and much more! Request our complete price list! Description: Robust frame welded construction made of thick-walled special profiles, sliding carriages, and pressure beams with 50 mm hole pitch. Continuous left-side abutment for width pressing, lower abutment on two levels. Vertical pressure cylinders on special pressure beams with single-hand quick adjustment and weight compensation, height-adjustable in 50 mm increments; long sliding carriages ensure sustained absorption of high pressing forces. Quick and smooth width adjustment via ball-bearing guide carriage with central locking, fixing in 50 mm increments. Upper horizontal pressure cylinder infinitely height-adjustable and equipped with weight compensation. Lower horizontal pressure cylinder with centering bores for both abutment levels, no weight compensation. Djdpfjd Ih H Ssx Aflewa Abutment and pressure plate depth 100 mm. Pressure plate and support width 130 mm. Machine controlled electro-hydraulically, with 2 vertical pressure cylinders, Ø 50 mm, stroke 120 mm, single-acting, with weight compensation and single-hand quick adjustment; 2 horizontal pressure cylinders, Ø 40 mm, stroke 120 mm, double-acting with weight compensation; 2 manual control valves, manometer, 1 pressure control valve from 20 to 100 bar corresponding to 400 to 2,000 kg pressing force vertically; powered by 3 kW three-phase motor for 400 V, 50 Hz operating voltage. Complete with electrical connection. Paint finish: RAL 7035 light grey with RAL 7016 anthracite grey. (Technical data according to manufacturer without guarantee, images may show optional equipment!)

Stanje: novo, Working width: 3,500 mm Working height: 2,300 mm Number of pressing cylinders: 4 pcs. S&S Frame Press Type T 35 – CE Version ----- Options: Working widths from 3,000 mm to 5,000 mm Working heights from 2,000 mm to 3,000 mm Optional equipment: center pressure beam, tilting window device, counter profiles for individual part production, and much more! Request the complete price list from us! Dodpfx Afjd Ih H Nslowa Description: Robust frame welded construction made of thick-walled special hollow sections, sliding carriages and pressure beams with 50 mm hole grid. Continuous left-side support for wide-veneer pressing; lower support on two levels. Vertical pressing cylinders mounted on special pressure beams with single-hand rapid adjustment and weight balance, height adjustable in 50 mm hole increments. Long sliding carriages ensure sustained absorption of high pressing forces. Fast, smooth width adjustment via ball-bearing carriages with central locking, fixation in the 50 mm hole grid. Upper horizontal pressing cylinder continuously height adjustable and equipped with weight balance. Lower horizontal pressing cylinder with centering holes for both support levels, without weight balance. Support and pressure plate depth: 100 mm Pressure plate and support width: 130 mm Electro-hydraulic machine control, with 2 vertical pressing cylinders d = 60 mm, stroke 120 mm, double-acting, with weight balance and single-hand rapid adjustment; 2 horizontal pressing cylinders d = 40 mm, stroke 120 mm, double-acting, with weight balance; 2 manual control valves, manometer, 1 pressure regulating valve from 20 to 130 bar equating to 550 to 3,500 kg vertical pressing force. With 3 kW three-phase motor for 400 V, 50 Hz operating voltage. Complete with electrical connection. Paint finish: RAL 7035 light grey with RAL 7016 anthracite grey. (Technical data according to manufacturer, subject to change. Image may show optional equipment!)

Stanje: novo, Leto izdelave: 2026, Trough Conveyor Belt | Troughed Belt Conveyor | Conveyor Belt Demonstration machine Manufacturer: S&F GmbH Model: MFB-500/8 Belt width: 500 mm Axle distance (A-A): 8,000 mm Throughput capacity: approx. 30 - 40 m³/h (at 0° incline) Drive: Drum motor Motor power: 2.2 kW, 400 V, 50 Hz Belt speed: approx. 1.25 m/s Dwedpfx Aexk Tg Noflja Drive drum: Drum diameter 220 mm Tensioning drum: Drum diameter 220 mm with spindle tensioning station Belt: Rubber steep-incline conveyor belt EP 250/2 2:1 with V-profile (32 mm) Machine weight: approx. 800 kg Machine color: RAL 6011 reseda green Suitable for, among others, the following bulk materials: Potatoes, wood chips, sawdust and wood shavings, biomass, wood pellets, charcoal, waste wood, bark, soil, humus, recycling material, cutoff pieces, and much more. Accessories (optional): Feed hopper (loading hopper), internal belt scraper, undercarriage, tow bar, steel support, electrical installation (plug switch 16 A) Trough conveyor belt | Troughed belt conveyor | Conveyor belt | Bulk material conveyor | Belt conveyor | Inclined conveyor belt

Stanje: novo, Leto izdelave: 2026, Trough conveyor belt | Troughed belt conveyor | Conveyor belt Demonstration machine Manufacturer: S&F GmbH Model: MFB-500/5 Belt width: 500 mm Centre distance (A-A): 5,000 mm Conveying capacity: approx. 30 - 40 m³/h (at 0° incline) Dodpfxsw Ad Rrj Aflowa Drive: Helical geared motor Motor power: 1.5 kW, 400 V, 50 Hz Belt speed: approx. 1.1 m/s Drive drum: Drum diameter 220 mm Tension drum: Drum diameter 220 mm with spindle tensioning station Belt: Rubber steep-angle conveyor belt EP 250/2 2:1 with V-profile (15 mm) Machine weight: approx. 450 kg Machine colour: RAL 6009 fir green Suitable for, among others, the following bulk materials: Wood chips, sawdust and wood dust, biomass, wood pellets, charcoal, waste wood, bark, earth, humus, recycling material, trimmings, and much more. Accessories (optional): Feed hopper, belt scraper, chassis, drawbar, steel support, electrical installation (plug switch 16 A) Trough conveyor belt | Troughed belt conveyor | Conveyor belt | Bulk material conveyor | Belt conveyor | Inclined conveyor belt

Leto izdelave: 2026, stanje: novo, Sejalni stroj | Vibracijski sejalni stroj tip ASM-550 Razstavni stroj - Znamka: S&F GmbH - Tip: ASM-550 - Kapaciteta sejanja: pribl. 60–70 m³/h (pri sekancih in žagovini) - Površina sita: 5,4 m² - Frakcije: 3 ali 4 - Sejalna nadstropja: 3 - Pogonska moč: 4,0 kW - Teža stroja: pribl. 3.800 kg - Barva stroja: RAL 6011 reseda zelena - Vložki sita in izpust materiala po izbiri Primeren mdr. za sejanje naslednjih razsutih materialov: - lesni sekanci in sekalni material - žagovina in lesni prah - biomasa - leseni peleti Dwedpfx Aextfv Ieflja - lesno oglje - odpadni les - lubje Vibracijsko sito | sito za sekance | vibracijski sejalni stroj | plansko sito | vibracijsko sito | valjčni separator | sejalni stroj za sekance

Leto izdelave: 2026, stanje: novo, Screening plant for loading wood pellets, semi-mobile Custom-built Screening capacity: 10 - 50 t/h (depending on configuration) Comprising: - Trough belt conveyor type TFB - Screening machine type ASM - Conveyor belt type MFB incl. magnetic separator - Loading fitting // MODULFLEX loader - Tubular screw conveyor (optional) - Deduster (optional) Functional description and operation: Pellets are fed into the trough belt conveyor (including hopper extension) using a wheel loader. The pellets then pass onto the vibration screening machine type ASM. The screening machine separates the pellets into two size fractions (pellets and dust). The screened pellets are loaded into the silo vehicle via a trough belt conveyor and loading equipment. Thanks to the integrated level sensor in the loading fitting, the unit shuts off automatically when the silo vehicle is sufficiently filled. The dust fractions are discharged by means of a screw conveyor. To minimize dust emissions, the screening unit can be equipped with an additional deduster type NE. The screening plant's capacity (depending on configuration) ranges from 10 to 50 t/h (70 m³/h) for wood pellets. Benefits: - High screening capacity - Precise separation efficiency - Low noise and low maintenance Djdpfx Afjiux Tfjlowa - Flexible application - Customized manufacturing Need more information? Contact us! We will be happy to advise you.

Leto izdelave: 2026, stanje: novo, Screening plant for wood chip screening Design: stationary or semi-mobile New production Screening capacity: approx. 20 - 40 m³/h (depending on model) Comprising: - Vibrating feeder bunker type AVB - Screening machine type ASM - Subframe / hook lift (optional) Dwodsin Ewlspfx Aflja - Conveyor belt type MFB - Electrical installation Function and operation: The wood chips are loaded into the vibrating feeder bunker with a wheel loader. They are then fed onto the vibrating screening machine type ASM. The screening machine separates the wood chips into three size fractions (oversize, chips, dust). The discharge of the fractions is handled by conveyor belts. Depending on the model, the screening plant achieves a capacity of 20 to 40 m³/h for wood chips. Advantages: - High screening capacity - High separation precision - Low noise and low maintenance - Flexible application - Custom manufacturing Do you require further information? Contact us! We will be happy to advise you.

Leto izdelave: 2025, stanje: novo, Screening plant for loading wood pellets, stationary New manufacture Screening capacity: 10 - 50 t/h (depending on configuration) Comprising: - Modular silo - Screening machine type ASM - Conveyor belt type MFB incl. magnetic separator - Loading set // MODULFLEX loader - Tubular screw conveyor (optional) - De-dusting unit (optional) Functional description and operation: The pellets are fed into the modular silo by wheel loader. The pellets are then conveyed onto the ASM vibrating screening machine. The screening machine separates the pellets into two fractions (pellets and fines). The screened pellets are loaded into the silo vehicle using a trough belt conveyor and loading set. Thanks to the integrated level sensor in the loading assembly, the system automatically switches off once the silo vehicle is sufficiently filled. Fines are discharged via a screw conveyor. To minimize dust exposure, the screening plant can be equipped with an additional NE de-dusting unit. Depending on the configuration, the screening plant achieves a throughput of between 10 - 50 t/h (70 m³/h) for wood pellets. Advantages: - High screening performance - Precise separation Dwsdpjinkw Asfx Afloa - Low noise and low maintenance - Flexible application - Custom manufacture Do you require further information? Please contact us! We will be happy to advise you. We look forward to your enquiry!

Leto izdelave: 2026, stanje: novo, Vibrating Screen Machine Series ASM S&F vibrating and flat screens are used in a wide range of applications throughout the wood processing industry (sawmills, pellet plants). The "ASM" series screening machines are used to screen wood chips, wood pellets, sawdust, reclaimed wood, biomass, and many other sawmill by-products in both dry and wet processing environments. The gentle, horizontally circular screening motion of the inclined screen box ensures high separation efficiency of this vibratory classifier. One key advantage is that long and fibrous particles slide diagonally or tangentially over the screen surface. As a result, in contrast with throw screens, there is no risk of clogging or pegging. Further advantages include a robust design, high throughput capacity, and long service life with minimal maintenance requirements. In addition to standard sizes, the company also offers the "ASM" series as a customized split version for existing installations. This allows new screening machines to be integrated even where space is tight or access is restricted, such as in existing plants or sawmills. ASM screening machines provide screening areas from 0.5 to 15 m² (per deck) and are characterized by high throughput capacities (up to 350 m³/h, depending on material). At a glance: - Ideal for: wood chips, pellets, sawdust, biomass, bark, reclaimed wood, substitute fuels - Application areas: wood industry, recycling & disposal, animal feed - Screening area: 0.5 – 15 m² (up to 30 m² as a double-deck version) Dedpfxsin Ey Se Aflewa - Throughput (material-dependent): up to 350 m³/h - Separation size: 0.1 – 150 mm (dependent on machine size) - Drive power: 0.55 – 15.0 kW (dependent on machine size) Advantages: - High throughput - High separation efficiency - No clogging or pegging - Quiet and low-maintenance operation - Versatile - Customized manufacturing Need more information? Contact us! We are happy to advise you.

Stanje: rabljeno, Magnetni ločnik S+S MES 40, premer 35 mm. Dwjdsmkig Uopfx Aflja Cena: 1.250 € Kontaktna oseba: gospod Rainer Eckerle.

Stanje: dober (rabljeno), Funkcionalnost: popolnoma funkcionalen, Lodret, isoleret tank i rustfrit stål med kølekappe, kapacitet 21.800 L. Udvendige mål: diameter Ø 2.500/2.600 mm, totalhøjde 6.500 mm. 3 stk. lodrette, isolerede rustfrie ståltanke med kølekappe. Bundmonteret mandehul. Udført i AISI 316 rustfrit stål. Dodpjv I Hbxsfx Aflewa

Leto izdelave: 2004, stanje: zelo dobro (rabljeno), Horizontal Bandsäge H+S 2600x600 mm Baujahr: 2004 Preis: 1.750 Euro Dwjdpfjin Nn Iex Afloa Ansprechpartner: Herr Rainer Eckerle

Stanje: rabljeno, Leto izdelave: 2018, Funkcionalnost: popolnoma funkcionalen, skupna dolžina: 7.120 mm, skupna širina: 1.020 mm, skupna višina: 800 mm, TAF-številka artikla: 1000003853 Proizvajalec: S-Serv Letnik izdelave: 2018 Skupne mere: pribl. 7.120 x 1.020 x 800 - 1.100 mm Širina z robom: 900 mm Višina roba: 90 mm Širina z pogonom: 1.020 mm Transportna dolžina: 7.070 mm Transportna širina: 800 mm Tip traku: PVC, gladek Širina traku: 800 mm Podkonstrukcija: vključno s podporniki H: 800 do 1.100 mm Pogon: čelni pogon Motor: motor z reduktorjem Podatki o motorju: SEW, 0,12 kW, 50-60 Hz, 230-400 Volt Dwsdpfxsr D Ntqj Aflsa Transportna hitrost: 0,1 m/s, konstantna Posebnosti: vključno s stranskim vodilom, H: 40 mm Stanje: Rabljeno / popolnoma funkcionalno Funkcionalni preizkus: OK

Stanje: rabljeno, 14 predalov, približno 2000 kg na predal. Globina podpore: 200 mm na predal. Širina: 6713 mm. Globina: 4200 mm. Višina: 2955 mm. Dedpfjxcv Akjx Aflowa

Stanje: zelo dobro (rabljeno), Steam washer for crates/containers 60x40 Brand: Maskinfabrikken Hillerslev a/s Plastic chain Belt width: 350 mm Dodpfx Asv Ey Ugjflswa Clearance: 650 mm x 200 mm Overall dimensions: 7300 mm x 1500 mm x 2000 mm

Stanje: dober (rabljeno), A-100730 - Horisontal tank 16 m3 Dwodpfsiiyufex Aflsa Horisontale tanke 16.000 L, Rustfrit stål AISI 316, Mål: Ø 2530 mm x H 2900 mm x L 3800 mm Mandørlåg foran

Stanje: dober (rabljeno), S+S metal detector for sorting metal parts from a material flow. The material passes through a chute, and the metal parts are separated and exit via a different chute. Chute inlet diameter: 70mm. Sold complete with its support frame, height 2m. Dwodpfjtu Nnuox Aflsa