Category Applied Science & Technology

Bond paper belongs to the class of paper called ‘writing’ paper. It is made of cotton rag pulp which gives it strength. It is also sized for opacity and toughness and the metallic sound. Bond paper is different in its non- absorbent qualities as it is well sized so as not to absorb water-based writing ink. It is also tough and strong due to rag content in the pulp.

The sizing may be animal or gelatin or tub sized as distinct from engine sizing used for printing paper. The word ‘bond’ owes its origin due to the fact that originally IOU’s or promissory notes (bonds) were widely using this rag content durable paper.

Smooth printing paper is used for photocopying to attract the toner powder. In the U.S, hardwood sulphite is beaten well and hydrated to produce bond paper. It produces crackle (sound) and results in a high mullen (tensile strength) bond paper which is water marked as ‘sunlit’, JK and ‘Executive’. They are used in making paper for insurance policies, stock certificates, bank notes and other important documents for longevity. There are machine dried and air dried bond papers. 

            

Not any more than eating enough of any other protein, according to dermatologists. If someone is severely protein-deficient, high-quality protein might make a difference, it is said. As an average person gets plenty of protein, it would take someone who was ‘malnourished or a food faddist, to see a real benefit.

 It’s the same case with calcium; it would help the nails if the person were totally deficient, but if one’s bones are falling apart the person would not care about their nails. To make a real difference in nail strength, it is said, they are to be treated as carefully as the skin is. If you moisturize your hands after you wash the dishes, for example, rub the product into the nails as well. Keep your nails out of harsh chemicals. Wear gloves to do housework.

People whose nails are really brittle might even wear latex gloves when washing hair. Nail polish and other drying nail care products are to be avoided. Polish covers nail abnormality but actually make it worse, according to them, but polish remover, even the kind without acetone, is incredibly drying to nails.

What if your nails split rather than break? There are two kinds of splitting, according to dermatologists. The longitudinal splitting is something that occurs with age. Ridges and valleys develop, and splitting occurs along fracture lines because the nails dry like the skin. Again, help for this problem lies in moisturizing. The nails are to be wet and covered with Vaseline or even alpha-hydroxyl acid, it is suggested. It is not a quick fix, but must be done until the nail grows out entirely which takes 6-8 months. The other kind of splitting, called onychoschisia, which occurs in layers at the tip of the nail, is something, dermatologists find most often ‘in chronic polishers or those who use fingernails as tools.’

Hairs are made of dead epithelial cells strengthened by a protein called keratin. Actually, epidermis (the upper layer of the skin) descend into the dermis (inner layer of skin) to form flask shaped structures. These structures hair follicles have a group of epithelial cells that form a bulb. Below this bulb is the dermal papilla or hair papilla which consists of connective tissue, supplied richly with blood vessels and connected by nerves. This region supplies nourishment to the root cells of the hair.

The epidermal cells of the hair root are very active and they divide rapidly. As new cells form, the old cells are pushed upwards in the form of hair.

Beyond the bulb region, the cells die and become horny with the addition of keratin. As the dead cells continue to add rapidly in the root, the shaft grows in length and pierces through the epidermal layer and projects out as hair. The hairs normally grow for about 18 cm in a year.

Thus the root is the only living part of the hair. Hence, when the hair above the skin is cut, we don’t feel any pain. But, if the hair is pulled out, because of the presence of the sensory nerves in the hair papilla, we feel the pain. A similar mechanism operates in the nail also. The root or matrix of the nail is made of soft epithelial cells and the growth takes place here as the cells are active and alive. As the cells grow the older cells are pushed out as the nail plate. Beyond the root region, the plate cells die and become horny again with keratin addition. Beyond the finger tip these horny cells project out as nails. From the root to the finger tip, the nail plate is connected to the underlying epithelial cells (nail bed), which are provided with blood vessels and nerves. When we pull this part out, we feel the pain, because the epithelial cells are also damaged. But beyond the finger tip, it is all dead cells and no pain is felt when cut. The nails grow to about 5 cm in a year.

Farm lands and fields are not smooth and hard like play grounds, and so the steering effort needed to be put in by a driver has to be more to drive a vehicle in them.

In case of tractors, the front wheels are meant for stability and steering only. They are small in size to aid in steering and to give a better view of the field to the driver. But the big rear wheels have specially designed tyres for an entirely different purpose – to give a better grip on the ground. Their larger surface areas in conjunction with a low air pressure (0.8 – 1.2 kg per square cm) ensure adequate contact area (and friction) between the tyre and the ground. This is necessary to increase the driving force in muddy fields.

If rear wheels are also small in diameter and width, their contact area with the soil surface will be small. This may, if the field is muddy, make the wheels penetrate and get bogged down in the mud, due to its own weight. If the wheels are large this cannot happen as a considerable amount of sand beneath the tyres has to be disturbed.

Lead in the form of tetra-ethyl lead (TEL) is added to petrol to suppress abnormal combustion called knocking.  High local pressure due to knocking results in excessive noise, power loss and eventual damage to petrol engines fitted to any motor vehicle – be it two, three, or four – wheeled vehicle. But the question posed apparently addresses two-stroke engines which are commonly used in two and three wheelers, accounting for nearly 60 percent of petrol consumption and discharging nearly 20 percent of raw petrol with lead directly into the atmosphere.

The unleaded petrol recommended for use in cars fitted with catalytic converters, can be safely used for any petrol vehicle. In fact, the use of unleaded petrol causes cleaner combustion without deposits on the chamber walls. These deposits caused by lead are known to hide raw petrol in their crevices and prevent them from combustion. These are discharged in the exhaust causing pollution besides higher fuel consumption. The engine also requires frequent decarbonising due to excessive deposits.

 In two stroke engines, the actual compression ratio is lower than the normal compression ratio, based on the ratio of cylinder volumes at the outer and inner dead centres, as the actual compression will not start until the piston covers the ports on the return stroke. So the probability of knocking in a two stroke engine with unleaded petrol is lesser than that in a four stroke engine of the same nominal compression ratio.

For leaded engines, the valves have to be coated with anti- corrosive materials and the piston rings need special treatment. Now comes the logical question: why not use unleaded petrol to all vehicles?

 Unfortunately, all our refineries are not geared up with modern refining methods like hydro-cracking or quality feed-stocks to produce lead-free anti-knock petrol (designated by high octane number) to meet the demands of all the petrol driven vehicles. The amount of lead depends on the fuel composition-paraffins with long chains needing most, the shorter and the branched chain hydrocarbons lesser and the aromatics the least or none, if the compression ratio is compatible.

In India, the limit fixed varies from 0.18 to 0.56 g/litre depending on the feed stocks available and the type of refining process infrastructure. Whatever unleaded petrol produced is only restricted to those cars plying in metropolitan cities which are mandatorily fitted with catalytic converters. Otherwise, leaded petrol will poison the catalysts. The problem of alternatives to leaded petrol is engaging the attention of the researchers for a long time. Natural gas or LPG is admirably suited as they are inherently knock-resistant because of their short chains.

Alcohols are also excellent knock -resistant fuels. Tertiary-butyl alcohol (TBA) and methyl tertiary-butyl ether (MTBE) have also been contemplated as additives.

 Lead poisoning is a serious health hazard. Many social organizations, worldwide, are making a study of this and are creating public awareness to this problem.

 The George foundation, a charitable and non-profit trust has pioneered a project ‘Lead Free’ in Bangalore and is collecting data in order to test and treat people severely affected by lead pollution. Hopefully, the project would be extended to other metropolitan cities. 

  There are 3 major reasons for a four-stroke engine of a two-wheeler being more eco-friendly than a two-stroke engine: In a two stroke engine, a part of the incoming air and fuel is short-circuited directly through the exhaust port of the cylinder and is carried away with the exhaust gases. This pollutes the atmosphere. But, the design of four-stroke engine is different there are valves (inlet and exhaust).

            Scavenging is effectively done in a four-stroke engine than in a two-stroke. (‘Scavenging’ is a process of removal of burnt gases from the engine cylinder.)

            If scavenging is not done properly, the residual burnt gas that inside the cylinder will be combusted again, this leads to smoky emission in two-stroke engines.

The lubrication system of a two-stroke engine is different from that of a four-stroke engine. In two-stroke engines, oil is mixed with the fuel (to provide lubrication for moving surfaces such as piston skirt and roller bearings). It is subsequently carried into the combustion chamber by the air stream, where it is partially burnt and partially pushed through the exhaust port, along with the exhaust gases. This results in smoky emission.

The suction, compression, expansion and exhaust strokes takes place in four strokes of the piston or two revolution of the crank shaft, in a four stroke engine

 In a two stroke engine compression and suction takes place in one stroke of piston and expansion and exhaust strokes also takes place in one stroke of piston. Hence in two strokes of piston all the four processes are completed which makes scavenging less efficient.

Scavenging is the process in which the products of combustion (i.e. burnt exhaust gases) are cleared from the cylinder and filling it with more or less completely with a fresh mixture of air and fuel. The incoming fresh mixture entering into the engine cylinder at certain velocity sweeps out the products of combustion from the cylinder.

 The fresh mixture entering acts as a scavenging or sweeping agent. But instead of acting as a sweeping agent, the fresh mixture also escapes through the exhaust port, as unburn hydrocarbons which are a pollutant.