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  1. How to Read a Vernier Scale
    April 08, 2021
    Vernier scales can be used on microscopes, stereotaxic frames and micromanipulators. The vernier scale was invented by French mathematician Pierre Vernier in 1631 as an upgrade on Pedro Nunes' measurement system for precision astrolobes. With a main scale and a sliding secondary scale, a vernier is used for making precise measurements.    How a Vernier Scale Works The vernier scale is marked with divisions slightly smaller than the divisions of the main scale. For example, a vernier scale could have 11 markings for every 10 on the main scale. That's 10 divisions on the vernier scale for every 9 on the main scale. This means that the vernier divisions are each 90% of the main scale divisions. In this case, the 0-line and the 10-line on the vernier could pair up with marks on the main scale, but none of the other divisions on the vernier would match a line of the main scale. For example, the 0 and 10-lines of the vernier scale could pair up with the 0 and 9-lines on the main scale. If the 0-line pairs up with a mark, the first division of the vernier (1 mark) would be 10% short of reaching a mark of the main scale, the second division (2 mark) would miss a mark on the main scale by 20%, the third division (3 mark) would miss a mark on the main scale by 30%, etc.   How to Read a Linear Vernier Scale Follow these steps to read the vernier scale: Read the main scale. Look for the last whole increment visible before the 0 (zero) mark. Read the secondary scale (Vernier) measurement. This is the division tick mark that lines up best with a mark on the main scale. Add the two measurements together. The image at the right shows a linear scale. The 0 on the vernier scale lines up with the 4 on the main scale. Notice that the 10 on the vernier scale also lines up with a mark on the main scale (4.9). We ignore the second mark that lines up. So, the measurement shown is 4.00mm. The second
  2. How Do I Select Appropriate Surgical Instruments for My Application?
    March 13, 2018
    When you are selecting surgical instruments for a procedure, here are a few key points to consider What procedure are you performing? Published research papers usually indicate which instruments other researchers have used for similar procedures. The correct surgical instrument for a particular procedure makes a difference on the outcome of that technique. What is the size of your subject? An instrument that is perfect for a 200­–300 g rat (about 22–25 cm long) may not be the best choice for a neo-natal mouse of about 15 g (about 1–2.5 cm long). How often will the instrument be used? If you perform more than 100 cuts per day, a pair of titanium scissors or a pair of scissors with tungsten carbide inserts would be worth considering. They stay sharp longer. In this article we will consider some of these factors and offer a few tips for selecting an appropriate pair of scissors, tweezers and forceps. Types of Surgical Instruments Most of our surgical instruments can be used for general surgery in a research laboratory setting. Instruments may be roughly categorized by function: Cutting instruments include scissors, surgical blades, knives and scalpels. Grasping or holding instruments include hemostatic forceps and tissue forceps. Retractors, which hold incisions open or hold an organ (or tissue) out of the way, include Gelpi, Weitlaner and US Army style instruments. In addition to surgical instruments, we have many accessories available, which include all the extras needed for surgery. These include clamps, from large towel clamps to delicate vessel clips and bulldog clamps, drills, sutures, binocular loupes, biopsy punches and more. Cutting Instruments 14003-G Vannas ScissorsScissors are cutting instrument with two blades joined together at a pivot point so that the sharp edges glide against each other to shear material that is between the blades. Here are some tips to keep in mind when selecting an appropriate pair of surgical scissors: Fine tip scissors (like Vannas, Castroviejos and McPhersons) are ideal for use in very restricted spaces. They are perfect for right or left hand use, and are designed for ophthalmological procedures, which require a delicate incision of tissue. You can make quick, accurate cuts with minimal tissue damage using these sharp blades. Curve tipped scissors are a good choice when you want to avoid cutting underlying tissues. Scissors designed with a heavier construction (like Metzenbaum, Mayo and SuperCut scissors) are useful for cutting fur, thicker tissue or vessels. 501745 Metzenbaum ScissorsThe length of the scissor tips should match the depth of the incision you need to make.  Scissors made with a heavier construction can be used to cut fur, thicker tissue, bones and muscle. 503261 Iris SuperCut ScissorsOur black handled surgical scissors designate our SuperCut scissors. These scissors have one on razor sharp blade and one micro-serrate blade. The sharp edge gives a clean cut with minimal tissue damage, and the serrated edge actually holds the tissue to prevent it from slipping while you are making an incision. Scissors with tungsten carbide inserts have golden handles. Tungsten carbide instruments are more durable, hold an edge longer and last longer than stainless steel instrument. Scissors with on black handle and one gold handle are both serrated and have tungsten carbide blade inserts, giving you the very best of both worlds. Spring scissors are perfect for left or right hand use. They are designed for neurosurgical, vascular, microsurgical and ophthalmological uses. 504075 Sapphire BladeSapphire blades may be used in microsurgery, dissection and related applications. They are not as hard as a diamond, but still hundreds of times harder then a razor blade. Sapphire blades can cuts with minimum pressure, without tearing or damaging the specimen. The blades are corrosion free and resistant to saline solution. They offer a super sharp cutting edge, and they work with stainless steel or titanium handles. These blades may be autoclaved up to 200ºC. Some common types of scissors include: Vannas scissors are delicate spring scissors, which are perfect for right or left hand use. They are used frequently in ophthalmic and neurosurgical applications. The fine scissor blades are sharp. Vannas scissors work well under a dissection microscope. Castroviejo scissors were designed for ophthalmologic procedures, which require a delicate incision of tissue. You can make quick, accurate cuts with minimal tissue damage using these sharp blades. McPherson-Vannas scissors were originally designed for ophthalmologic work requiring fine delicate blades for such intricate work. Vannas Scissors Castroviejo Scissors McPherson-Vannas Scissors Grasping Instruments Surgical forceps may be broadly divided into two categories, ring forceps (also called hemostats, hemostatic forceps and locking forceps) and thumb forceps (frequently called tweezers or pinning forceps). Here are some tips to keep in mind when selecting an appropriate pair of forceps: Reverse forceps are self-closing. You squeeze them to open them. They provide uniform tension. Ceramic tipped forceps are non-porous, corrosion and heat resistant and insulated. Straight tips on forceps are used for general precision work, and slightly curved or fully curved tips provide more visibility Reverse Forceps Ceramic Tipped Forceps   15921 Halsted Mosquito ForcepsRing forceps, also called hemostats or locking forceps, are an instrument for grasping, holding firmly or exerting traction upon objects especially for delicate operations. They are hinged and look like ring scissors. Frequently, hemostatic forceps have a locking mechanism called a ratchet, which is used for clamping. The jaws of the locking forceps gradually come together as each increment of the ratchet is employed. Locking hemostatic forceps may be called clamps and are used to securely hold tissue. When they are used to control blood flow, they are called hemostats. Hemostats are typically used to compress blood vessels or other tubular structures to obstruct the flow of blood or fluids. Common types of ring forceps include: Kelly hemostats can be used to clamp larger vessels or grasp tissue. Kelly hemostats and Rochester forceps look similar. However, Kelly hemostats have shorter serrations. Rochester hemostats can reach a little deeper. Kelly-Rankin Hemostats Rochester-Oschner Hemostats Hartman Mosquito forceps have fine, short tips and a serrated jaw. Hartman Mosquito hemostats are used as hemostats for clamping small blood vessels and in fine tissue dissection when the incision is shallow. Use them to clamp small blood vessels or hold fine sutures. For a lighter and longer hemostat, try the Halstead Mosquito Forceps. Hartman Mosquito Forceps Halstead Mosquito Forceps Allis tissue forceps have sharp teeth for gripping heavy tissue. Because they can cause damage, they typically hold tissue that is to be removed. Crile hemostats are similar to Halsted Mosquito forceps, but they are a little larger. Rochester-Oschner forceps are heavy hemostats designed for clamping large vessels or grasping dense tissue. They are serrated for grasping and often have teeth at the tip, too. Stars and stripes tips of Rochester-Carmalt forcepsRochester-Carmalt forceps, nicknamed the "stars and stripes hemostat," are characterized by the longitudinal serrations that run the length of the blade with cross-hatching at the tip. These large, crushing hemostatic forceps are a choice instrument for clamping blood vessels and large tissues or ligating pedicles. Rochester-Pean hemostatic forceps are designed with full horizontal serrations for clamping larger tissue and vessels.  Rochester-Oschner Forceps  Rochester-Carmalt Forceps Rochester-Pean Thumb forceps are spring forceps used by compression between your thumb and forefinger and are used for grasping, holding or manipulating body tissue. They have no ratchet in the handle. Two broad categories of thumb forceps are dressing forceps and tissue forceps. Dressing forceps are used when dressing wounds and removing dressings. Very fine dressing forceps are also used in eye surgery. Tissue forceps generally have teeth, which offer a better grip on tissues while minimizing tissue damage. Common types of thumb forceps include: Adson tissue forceps are designed for grasping delicate tissues, and they have 1x2 teeth. Bonn tissue forceps are designed for delicate work, and they include a tying platform to assist when you are tying sutures.  Adson Tissue Forceps Bonn Tissue Forceps  Foerster tissue forceps work well when handling delicate tissue. These serrated forceps have the unique octagonal keyhole in the handle, giving your tactical feedback and control. The keyhole also gives you a better grip, especially when you are wearing gloves. When you need a firm grip and minimal tissue trauma, the Foerster forceps are an excellent choice. Iris forceps are designed for use in ophthalmologic work. The Iris dressing forceps are serrated and the Iris tissue forceps have 1x2 teeth. Graefe forceps have a horizontal row of 6 (or 8) small teeth for grasping tissue. They are most commonly use in ophthalmologic applications.   Iris Dressing Forceps
  3. Ca2+ Detection in Muscle Tissue using Fluorescence Spectroscopy
    June 27, 2017
    The use of fluorescent probes in cell physiology has emerged as indispensable tool in the analysis of cell functioning over recent years. The physics underlying fluorescence is illustrated by the electronic-state diagram (so-called Jablonski diagram, see Fig. 1), showing the three-stage process to create the fluorescent signal (Excitation - Excited/State Lifetime - Fluorescence Emission) in a fluorophore/indicator and simplified described below. Fig. 1– Jablonski diagram illustrating the processes of fluorescence by absorption of higher photon energy by a fluorophore and subsequent emission of lower photon energy, resulting in fluorescence during the fluorescence-lifetime.   Fluorescence is obtained when an excitation photon (hνEX) from an external source, such as a high-power LED, is absorbed by a fluorophore that elevates its energy (S1’). During the fluorescence-lifetime, the elevated energy (S1’) decays to a lower energy state S1. Then, fluorescence results in the emission of a photon with lower energy (hνEM) and therefore of longer wavelength. Fundamental in spectroscopy is the difference in energy or wavelength represented by (hνEX-hνEM), which is called the Stokes shift. The Stokes shift allows efficient discrimination of the excitation, making fluorescence a very sensitive technique and able to be detected against a low background, isolated from excitation photons.   Fig. 2– Typical excitation-emission diagram, showing the absorbance spectrum of a molecule at shorter wavelength (i.e. higher energy) from a corresponding excitation source and the resultant fluorescence spectrum of the emitted light at longer wavelength (i.e. lower energy state).  Four essential elements of fluorescence signaling can be then iden
  4. Detection of organic compounds in water analysis
    June 27, 2017
    Absorption of light correlates to the energy of a photon that is taken-up by electrons of the substance atom. The electromagnetic energy is transformed into internal energy of the absorbent substance. The absorbance of a substance quantifies how much of the incident light is absorbed by it (instead of being reflected or refracted). Precise measurements of the absorbance at many wavelengths allow the identification of a substance via absorption spectroscopy, where a sample is illuminated from one side, and the intensity of the light that exits from the sample in every direction is measured (see Fig. 1). A few examples of absorption are ultraviolet–visible (UV-Vis) spectroscopy or infrared (IR) spectroscopy. Fig 1. Concept of absorbance spectroscopy using white light and optical components to filter out light of a specific wavelength that interacts with molecules in the solution. Absorbance at this specific wavelength by the molecules in the solutions is detected as a decrease in light intensity (Spectrophotometer-Source: http://chemwiki.ucdavis.edu/). Absorption is the amount of light that a substance takes in and does not allow to pass through it. Spectrophotometers actually measure transmission, the amount of light that passes through a sample, but this is converted into absorption by comparing the bulb output to the light that has passed through the sample. Light sources that can be used for absorbance spectroscopy depend strongly on the used substance to label a specific molecule and can span the entire electromagnetic spectrum of light. Industrial applications that cover the UV spectrum for protein detection is linked to food analysis (for example, characterizing the grading of olive oil as extra virgin, virgin oil, etc., as set out by European regulations) or quality control in the pharmaceutical industry. In addition, industrial applications of absorbance spectrophotometry cover the characterization of water purity or waste water analysis, in addition to the determination of specific or
  5. Surgical Loupes Defining Differences
    May 01, 2013
    Surgical Loupes help to alleviate eye strain by enlarging the image when you are working on tiny subjects or conducting precision operations. They are portable and easier to use than a surgical microscope. However, they are not created equal, and choosing the pair that's right for you is important to your satisfaction. See Selection Factors Involved in Choosing Loupes Choosing the correct surgical loupes for your application involves several factors, including resolution, working distance, field of view, depth of field,  magnification, weight and interpupillary distance. These terms are defined below. Ideally, you want the lowest magnification that is suitable for your application. As a general rule, the lower the magnification, the greater the depth of field and field of vision. Likewise, the longer the working distance, the greater the field of view. The larger your field of view, the less you need to turn your head. This reduces eye strain and fatigue. It is also important to consider the weight and fit of your loupes. Lightweight loupes are more comfortable for longer periods of use, and they are less likely to slide down your nose as you work. WPI loupes have adjustable interpupillary distance for a correct fit every time. Three styles of loupes are available today. The first is a single lens loupe for simple, low-magnification
  6. Z-Dimensions Are Not Created Equal
    May 01, 2013
    Cuvettes come in a variety of shapes and sizes, but one of the most important specifications of a cuvette is its Z-dimension. The Z-dimension of an instrument (cuvette holder or spectrometer) is the distance from the bottom of the cuvette chamber floor to the center of its light beam (see image). A cuvette’s Z-dimension must match the Z-dimension of the instrument with which it will be used. Each manufacturer designs its instruments with a specific Z-dimension. Common Z-dimensions include 8.5 and 15mm, and sometimes 20mm. When purchasing small volume cuvettes, the correct Z-dimension becomes critical. Matching the Z-dimension of the cuvette to the Z-dimension of the instrument ensures that the light beam passes through the center of small samples.The table below shows the standard Z-dimension of the spectrometer sample compartments for many manufacturers.
  7. WPI's Low-Noise Amplifiers Outperform Cheap Imitations
    April 30, 2013
    An amplifier, in simplest terms, is an electronic device that magnifies an input signal. However, the way an amplifier is designed to handle noise and bandwidth limitations greatly affects the quality and sustainability of the final output signal. Defining Terms To knowledgeably discuss amplifiers, let’s define a few terms. Gain – The gain is the multiplier defining how much the amplitude of an input signal is increased. A signal with an X1 gain is not amplified. An X10 gain produces an output signal ten times greater than the input signal. Noise – Any unwanted signal fluctuations are called noise. While noise can also result from external sources, for the purpose of this discussion, we are primarily concerned with the noise resulting from the inner workings of the electronic device, our amplifier. This
  8. Which Alloy is Best for My Surgical Instruments?
    April 30, 2013
    Inox, Titanium, Dumoxel®, Dumastar®, Antimagnetic... Have you ever looked at the variety of metal alloys for surgical instruments and laboratory tools and wondered which is best for your needs? Here's a brief rundown. Stainless Steel (Inox) - Our standard line of instruments are manufactured of highest quality materials, they are made of austenitic 316 steel commonly known as “surgical steel” or “marine grade steel.” Stainless steel, also known as Inox (from the French word "inoxydable"), is highly corrosion resistant and it is a common choice of material for biomedical implants or body piercing jewelery. It is in compliance with ASTM F138. This WPI line is an excellent alternative to German surgical instruments. The high-quality, corrosion-resistant instruments are available at a fraction
  9. DLC Coating Multiplies Useable Life of Surgical Instruments
    April 29, 2013
    When applied to surgical instruments, Diamond-Like Carbon coating dramatically increases the life of the instrument. Because DLC-coated surgical instruments are incredibly durable and resistant to wear from chemicals, moisture and atmospheric conditions, they have a much greater useful lifespan. According to the manufacturer, pure DLC coatings as thin a 2-3μm can increase the lifespan of a pair of Vannas scissors more than 100 times that of its uncoated counterpart. DLC is a revolutionary new coating that is being tested in a variety of industries. For example, when engine parts are coated, the DLC reduces friction and corrosion, increasing the life of the engine. In a completely different industry, DLC coating is being tested on metal heart valves. The coating is non-toxic, and it is so slick that biological
  10. What's the Difference Between a 3-way and 4-way Stopcock?
    April 26, 2013
    A 4-way stopcock allows for 360° of rotation and has the states (shown below) for each of the four available positions. A 3-way stopcock has only three positions and has the first three states shown below. In the first state, liquid flows between points A and B.In the second, it flows between points A and C.In the third, it flows between points B and C.In the fourth state (4-way only), it flows between all three points.    3-way and 4-way stopcocks are sold in the popular kit 14011. They can also be bought separately: 14035-10
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