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By H. Oelk. Principia College.

When initiating treatment with risperidone depot injection buy kamagra super on line amex, oral risperidone (or the patient’s previous antipsychotic if not risperidone) should also be provided for the first 3 weeks after the first injection buy 160 mg kamagra super fast delivery. Patients stabilised more than 4mg oral risperidone daily for at least 2 weeks: initiate therapy at 37 cheap kamagra super 160mg with mastercard. Maintenance therapy: increase the dose if necessary at intervals of at least 4 weeks in steps of 12 order 160 mg kamagra super with visa. Risperidone long-acting injection | 741 Intramuscular injection Preparation and administration 1. The pack should be removed from the refrigerator and allowed to come to room temperature before reconstitution. Follow the manufacturer’s instructions to reconstitute the vial with the diluent provided to give a thick,milkysuspensioncontaining25mg/2mL,37. For gluteal administration use a 50-mm needle and alternate injections between the buttocks; for deltoid administration use a 25-mm needle and alternate between the arms Technical information Incompatible with Not relevant Compatible with Not relevant pH 6. If refrigeration is not available the product may be stored below 25 C for up to 7 days prior to administration. Stability after From a microbiological point of view, should be used immediately; however, preparation reconstituted suspension may be stored at 25 C for up to 6 hours. Shake the syringe vigorously to re-suspend the microspheres before administration. Monitoring Measure Frequency Rationale Therapeutic effect During dose adjustment * To ensure reduction/elimination of and periodically psychotic symptoms. Additional information Common and serious Weight gain, depression, fatigue and extrapyramidal symptoms. If the patient is in shock, treatment with metaraminol or noradrenaline may be appropriate. Counselling Advise patients not to drink alcohol especially at the beginning of treatment. May impair alertness so do not drive or operate machinery until susceptibility is known. This assessment is based on the full range of preparation and administration options described in the monograph. ClinicalGuideline82:Coreinterventionsinthetreatmentand management ofschizophreniain primary and secondary care (update). Pre-treatment checks * Caution in patients with a history of cardiovascular disease because exacerbation of angina, arrhythmia, and heart failure have been reported. Administer only in an environment where full resuscitation facilities are immediately available. Inspect visually for particulate matter or discolor- ation prior to administration and discard if present. Observe for mild infusion-related * #Infusion rate usually resolves reactions: fevers, chills rigors these symptoms. Respiratory function * In patients with pre-existing pulmonary conditions or in whom adverse pulmonary events have occurred at previous infusions. Infusion-related: Occur predominantly during the first infusion and include cytokinereleasesyndrome(see Monitoringabove),feverandchills,nausea and vomiting, allergic reactions (such as rash, pruritus, angioedema, bronchospasm and dyspnoea), flushing and tumour pain. Actionincaseof overdose There is no specific antidote and treatment should be symptomatic. Counselling Any vaccination schedule should be completed at least 4 weeks prior to the first treatment. This assessment is based on the full range of preparation and administration options described in the monograph. Premature labour: glucose is the preferred diluent and use of a syringe pump is the preferred means of administration ("risk of maternal pulmonary oedema if saline or large volumes of fluid are used). However, this use is controversial as it is reportedly no more effective than 10--20mg nebulised salbutamol and may be more likely to cause cardiac arrhythmias. If effective, #K levels are seen in 30 minutes and the effect may last for up to 2 hours. Inspect visually for particulate matter or discoloration prior to administration and discard if present. Continuous intravenous infusion (large volume infusion) Preparation of a 20 micrograms/mL solution 1. Using the 5mg/5mL strength of salbutamol, withdraw 10mg (10mL) and add to the prepared infusion bag to give a solution containing 20 micrograms/mL. Inspect visually for particulate matter or discoloration prior to administration and discard if present. Inspect visually for particulate matter or discoloration prior to administration and discard if present. Stability after From a microbiological point of view, should be used immediately; however, it preparation may be stored at 2--8 C and infused (at room temperature) within 24 hours. Monitoring Measure Frequency Rationale Respiratory function Frequently * For signs of clinical improvement. Significant * Beta-blockers (including eye drops) may #salbutamol levels or effect. This assessment is based on the full range of preparation and administration options described in the monograph. Selenium 50 micrograms/mL solution in 2-mL and 10-mL ampoules * Selenium is an essential trace element that acts as a co-factor in various enzymes in the human body. Inspect visually for particulate matter or discolor- ation prior to administration and discard if present. Technical information Incompatible with A precipitate forms if the pH falls below 7 and if the solution is mixed with reducing substances, e. Monitoring Measure Frequency Rationale Selenium level Periodically * For signs of clinical improvement. Additional information Common and serious None known undesirable effects Pharmacokinetics Elimination is dependent on the selenium status of the body. Chronic overdose can affect growth of nails and hair and may lead to peripheral polyneuropathy. Antidote: Forced diuresis or the administration of high doses of ascorbic acid may be of use. In the case of an extreme overdose (1000--10000 times the normal dose) dialysis may help. This assessment is based on the full range of preparation and administration options described in the monograph. Pre-treatment checks Do not use in pregnancy, or severe renal or hepatic disease, a history of blood disorders, exfoliative dermatitis, systemic lupus erythematosus, necrotising enterocolitis, pulmonary fibrosis or porphyria. The dose frequency may then be reduced to every 2 weeks until full remission occurs and then further reduced on specialist advice. If thereisno evidenceof improvement after atotaldose of1g has beengiven, andifthere arenosigns of gold toxicity,then100mg may be giveneveryweekfor 6weeks. Technical information Incompatible with Not relevant Compatible with Not relevant pH Not relevant (continued) 752 | Sodium aurothiomalate Technical information (continued) Sodium content Negligible Storage Store below 25 C in original packaging. Skin inspection * Rashes often occur after 2--6 months of treatment and may necessitate stopping treatment. Medical observation For a period of 30 * Anaphylactoid reactions have been reported. Additional information Common and serious Immediate: Anaphylaxis and other hypersensitivity reactions have been undesirable effects reported. Other: Severe reactions (occasionally fatal) in up to 5% of patients; mouth ulcers, skin reactions, proteinuria, blood disorders, irreversible pigmentation in sun-exposed areas. Pharmacokinetics Elimination half-life is 5--6 days; this can increase with multiple doses and gold may be found in the urine for up to 12 months owing to its presence in deep body compartments. Counselling The patient is to tell the doctor immediately if sore throat, fever, infection, non- specific illnesses, unexplained bleeding and bruising, purpura, mouth ulcers, metallic tasteorrashesdevelop. Risk-reduction strategies should be considered This assessment is based on the full range of preparation and administration options described in the monograph. It is reabsorbed by the kidney following glomerular filtration and this action is balanced by the excretion of hydrogen ions to maintain the systemic pH. Allow natural compensatorymechanisms tomakethe final approach tonormalacid--base balance. Correction of acidosis during advanced cardiac life support: routine use is not recom- mended. Repeat the dose according to the clinical condition of the patient and the results of repeated blood gas analysis.

A number of case reports document children who developed either congenital or late-onset hypothyroidism after their mothers were treated with 131I during various stages of pregnancy (Fisher et al discount kamagra super 160mg fast delivery. Maternal hypothyroidism Untreated hypothyroidism can impair fertility and increase the incidence of spontaneous abortion buy kamagra super no prescription, stillbirth discount 160mg kamagra super free shipping, and congenital anomalies (Davis et al purchase kamagra super with american express. Possible causes of hypothyroidism include iodine deficiency, iatrogenic (thyroidectomy or 131I therapy) or thyroiditis. Symptoms include cold intolerance, irritability, difficulty with concentration, dry skin, coarse hair, and constipation. Clinical diagnosis may be difficult because many of these symptoms are commonly seen in normal pregnancy. Several reports suggest that it is not a major cause of con- cern (Kennedy and Montgomery, 1978; Montoro et al. The frequency of con- genital anomalies was not increased among 537 pregnancies exposed to exogenous thy- roxine or thyroid hormone during the first trimester, and 1605 pregnancies exposed at any time during pregnancy (Heinonen et al. Evidence indi- cates no increased risk of congenital anomalies in infants whose mothers used liothyro- nine during pregnancy (Heinonen et al. Pregnant women require three to four times the nonpregnant daily requirement for calcium, particularly during the latter half of gestation when most of the fetal bone mineral is deposited. Maternal 1,25 dihydroxy vitamin D levels and intestinal absorption of calcium increase markedly (Bouillon and Van Assche, 1982; Heany and Skillman, 1971; Kumar et al. Maternal hyperparathyroidism Secretion of excess parathyroid hormone during pregnancy causes increased bone resorp- tion and serum calcium, and other clinical manifestations similar to those in the nonpreg- nant state. Gravidas may seem asymptomatic; however, 80 percent present with general- ized muscle weakness, nausea, vomiting, pain, renal colic, and/or polyuria. Primary hyper- parathyroidism is most frequently caused by an adenoma in one of the inferior parathy- roid glands. An unusually high frequency of hyperparathyroidism was reported among women with a history of irradiation to the head or neck in childhood (Gelister et al. Maternal effects include an increased incidence of renal stone formation caused by hypercalciuria, hyperphosphaturia, and thinning of bone tra- beculae, secondary to increased bone resorption (Peacock. Embryo and fetal effects include a high incidence of spontaneous abortion, stillbirth, neonatal death, and low birth weight (Delmonico et al. The inci- dence of severe hypocalcemia and tetany in infants born to mothers with hyperparathy- roidism approaches 50 percent (Butler et al. Infants are usually unable to maintain normal serum calcium concentration in the perinatal period. Neonatal calcium supplementation is needed, but this effect is transient and usually resolves by 2 weeks of age without sequelae (Pederon and Permin, 1975). Treatment of choice for primary hyperparathyroidism during the pregnant or non- pregnant state is surgery to avoid maternal, fetal, and perinatal complications. Symptoms are similar to the nonpregnant state, including weakness, fatigue, tetany (by Chvostek’s and Trousseau’s tests) and seizures. The etiology is usually idio- pathic, autoimmune or iatrogenic (parathyroid glands removed or blood supply com- promised during thyroid surgery). Untreated maternal hypoparathyroidism is associated with neonatal hyperparathyroidism, hypercalcemia, and osteomalacia (Aceto et al. Symptoms are transient and normally resolve over time (Landing and Kamoshita, 1970). Along with cal- cium, vitamin D is used to treat hypoparathyroidism in both the pregnant and nonpreg- nant state. Pregnant patients treated for hypoparathyroidism with vitamin D apparently do not have an increased incidence of embryotoxic effects or fetal malformations (Goodenday and Gordon, 1971a,b; Sadeghi-Nejad et al. Pituitary disorders that may complicate pregnancy include: enlargement of a prolactin- oma, acromegaly, Cushing’s disease, and diabetes insipidus. Prolactinoma The pituitary gland enlarges during pregnancy and the presence of prolactinoma and its enlargement in pregnant women is a concern. A review of 16 investigations and 246 patients revealed a low incidence of symptomatic microadenoma (less than 10 mm in size) enlargement of 1. However, maternal plasma oxytocin and vasopressin levels are low and do not vary throughout gestation (Fisher, 1983b). Bromocriptine crosses the placenta and is associated with fetal hypoprolactinemia (del Pozo et al. Outcomes of 1410 pregnancies in 1135 women who received bromocriptine in the early weeks of pregnancy was associated with a higher frequency of spontaneous abortion (11. Children (n = 212) from this study who were followed for up to 5 years were normal on mental and physical development assessments. Similar findings with fewer patients were reported by other investigators (Canales et al. Evidence indicates that there is no increased risk to the fetuses of women treated with bromocriptine dur- ing pregnancy, and if symptomatic tumor enlargement should occur, bromocriptine ther- apy is preferred to surgical intervention (MacCagnan et al. The most common cause is a pituitary ade- noma, and therapy often consists of surgery, radiation, medical therapy, or some combina- tion. Menstrual irregularity (amenorrhea) is frequent and fecundity is low in acromegalic women. Symptomatic tumor expansion may arise during gestation as a result of increased maternal estrogen levels (Yap et al. Optimal management is conservative and definitive ther- apy is preferably postponed until after delivery. Hence, Cushing’s disease refers simply to pituitary-dependent Cushing’s syn- drome. The etiology of Cushing’s syndrome is usually a pituitary adenoma or hyperplasia, and during pregnancy the frequency of primary adrenal lesions is much higher (Gormley et al. Pregnancy is very uncommon among women with Cushing’s syndrome because most such patients are amenorrheic (Gormley et al. The diagnosis may be difficult because many of the symptoms (hypertension, weight gain, fatigue, striae, and increased pigmentation) are common in normal pregnancies. Thinning of the skin, spontaneous bruising and muscle weakness are symptoms more specific of Cushing’s syndrome. Hirsutism and acne are common in pregnant women with Cushing’s syndrome because of increased adrenal androgens (Grimes et al. Pregnancy out- come is extremely poor, with approximately 50 percent of gestations ending in sponta- neous abortion, premature delivery or stillbirth (Aaron et al. Treatment depends on the etiology of the disorder and the stage of pregnancy at diagnosis. Pituitary and adrenal adenomas should be removed surgically (van der Spuy and Jacobs, 1984). In the first trimester, pregnancy termination may be consid- ered, especially if adrenal carcinoma is suspected. In late gestation, medical therapy with metyrapone may be considered until delivery of the infant, after which definitive surgery may be undertaken. This is followed by a subsequent rise of desoxycortisol, the immediate precursor of cortisol. Animal studies have shown that metyrapone does cross the placenta (Baram and Schultz, 1990). Metyrapone has been used infrequently during late pregnancy as medical therapy for Cushing’s disease to delay surgical intervention until after delivery (Connell et al. In summary, the ideal therapy for Cushing’s disease in pregnancy is surgical intervention. Clinical characteristics are polyuria, excessive thirst, polydipsia, and low urinary specific gravity. The etiology is idiopathic, inherited as autosomal dominant, or secondary to trauma or tumor. Patients with dia- betes insipidus who are successfully treated do not have impaired fertility, and fetal out- come is not adversely affected by the disease (Hime and Richardson, 1978; Jouppila and Vuopala, 1971). Other modes of therapy in the patient with partial diabetes insipidus are not recom- mended for use during pregnancy (chlorpropamide, clofibrate, and carbamazepine). There is a two- to three-fold increase in plasma-unbound cortisol coupled with a two-fold increase in free cortisol excretion (Clerico et al. In spite of the elevation of free cortisol in pregnancy, clinical evi- dence of cortisol hypersecretion is not seen (Gibson and Tulchinsky, 1980). Increased renin activity is associated with elevated aldosterone levels, although this does not appear to be clinically significant (Smeaton et al.

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A number of different mechanisms behind the barrier-improving effects from moisturizers have been suggested quality 160 mg kamagra super. Moreover purchase 160 mg kamagra super visa, it is possible that the applied moisturizer decreases the proliferative activity of epidermis order kamagra super amex, which increases the size of the corneocytes cheap kamagra super 160mg otc. With a larger corneocyte area, the tortuous lipid pathway gives a longer distance for penetration, which reduces the permeability (58,124,198). Reduction in mi- totic activity and cell proliferation has been found by treatment with lipids and urea (199–201). Topically applied lipids may also penetrate deeper into the skin and inter- fere with endogenous lipid synthesis, which may promote, delay, or have no obvious influence on the normal barrier recovery in damaged skin (90,126). Other mechanisms, such as anti-inflammatory actions, are also conceivable explanations to the beneficial actions of moisturizers on the skin. In conclusion, we can foresee that the increased understanding of the inter- actions between topically applied substances and the epidermal biochemistry will improve the formulation of future skin care products (202). Furthermore, nonin- vasive bioengineering techniques will allow us to monitor treatment effects more closely and in the future we can also expect new devices that can diagnose specific skin abnormalities noninvasively. Evaluation of the hydration and the water-holding capacity in atopic skin and so-called dry skin. In vivo hydration and water-retention capacity of stratum corneum in clinically uninvolved skin in atopic and psoriatic patients. Func- tional analysis of the hygroscopic property and water-holding capacity of the stra- tum corneum in vivo and technique for assessing moisturizing efficacy. Hydration characteristics of pathologic stra- tum corneum-evaluation of bound water. The water-binding capacity of stratum corneum in dry non-eczematous skin of atopic eczema. The increase in skin hydration after application of emollients with differ-´ ent amounts of lipids. Effects of single application of a moisturizer: Evaporation of emulsion water, skin surface temperature, electrical conductance, electrical capacitance, and skin surface (emulsion) lipids. Characterizing cosmetic effects and skin morphology by scanning electron microscopy. Instrumental and sensory evaluation of the frictional response of the skin following a single application of five moisturizing creams. Changes in the physical properties of the stratum corneum following treatment with glycerol. Evaluation of hydration state and surface defects in the stratum corneum: Comparison of computer analysis and visual appraisal of positive replicas of human skin. Clinical and non-invasive evalu-´ ´ ation of 12% ammonium lactate emulsion for the treatment of dry skin in atopic and non-atopic subjects. Topographics of dry skin, non-dry skin, and cosmetically treated dry skin as quantified by skin profilometry. Effect of a skin cream containing the sodium salt of pyrrolidone carboxylic acid on dry and flaky skin. Further observations on factors which influence the water content of the stratum corneum. Structure of fully hydrated human stratum corneum: a freeze-fracture electron microscopy study. Urea and retinoic acid in ichthyosis and their effect on transepidermal water loss and water holding capacity of stratum corneum. Investigation of Cortesal, a hydrocortisone cream and its water-retaining cream base in the treatment of xerotic skin and dry eczemas. Ichthyosis vulgaris: identification of a defect in filaggrin synthesis correlated with an absence of keratohyaline granules. The concentration of pyroglutamic acid (2-pyrroli- done-5-carboxylic acid) in normal and psoriatic epidermis, determined on a micro- gram scale by gas chromatography. Denda M, Hori J, Koyama J, Yoshida S, Nanba R, Takahashi M, Horrii I, Yama- moto A. Stratum corneum sphingolipids and free amino acids in experimentally- induced scaly skin. A new method to evaluate the softening effect of cosmetic ingredients on the skin. The effect of urea on the skin with special reference to the treatment of ichthyosis. The distribution and keratolytic effect of sali- cylic acid and urea in human skin. Effect of 2-hydroxyacids on guinea-pig foot- pad stratum corneum: mechanical properties and binding studies. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. Prevention of model stratum corneum lipid phase transitions in vitro by cosmetic additives—Differential scanning calorimetry, optical microscopy, and water evapo- ration studies. Prevention of stratum corneum lipid phase transitions in vitro by glycerol—An alternative mechanism for skin moisturization. Mammalian epidermal barrier layer lipids: compo- sition and influence on structure. Percutaneoustransport inrelationtostratum corneum structure and lipid composition. A possible function of structural lipids in the water-holding properties of the stratum corneum. Importance of intercellular lipids in water-retention properties of the stratum corneum: induction and recovery study of surfactant dry skin. Exogenous lipids influence permeability barrier recovery in acetone-treated murine skin. A new in vitro method for transepi- dermal water loss: A possible method for moisturizer evaluation. The in-vitro percutaneous absorption of glycerol trioleate through hairless mouse skin. Transepidermal water loss and water content in the stratum corneum in infantile seborrhoeic dermatitis. Correction of essential fatty acid deficiency in man by the cutaneous application of sunflower-seed oil. The repair of impaired epidermal barrier function in rats by the cutaneous application of linoleic acid. Selective recovery of deranged Moisturizers 91 water-holding properties by stratum corneum lipids. Dietary supplementation with ethyl ester concentrates of fish oil (n-3) and borage oil (n-6) polyunsaturated fatty acids induces epidermal generation of local putative anti-inflammatory metabolites. Anti-inflammatory effects of eicosapentaenoic acid on experimental skin inflammation models. Highly purified omega- 3-polyunsaturated fatty acids for topical treatment of psoriasis. Effect of di- etary supplementation with n-3 fatty acids on clinical manifestations of psoriasis. A randomized, double blind, placebo-controlled study to evaluate the effect of fish oil and topical corticosteroid therapy in psoriasis. Dietary supple- mentation with very long-chain n-3 fatty acids in patients with atopic dermatitis. Atopic eczema unresponsive to evening primrose oil (linoleic and α- linolenic acids). Atopic eczema unresponsive to evening primrose oil (linoleic and α-linolenic acids). Double-blind, multicentre analysis of the efficacy of borage oil in patients with atopic eczema. Transepidermal water loss in dry and clinically normal skin in patients with atopic dermatitis. Stratum corneum lipid morphology and transepidermal water loss in normal skin and surfactant-induced scaly skin.

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The relationship between the torr and several of the other units used to measure pressure follows: 1 torr 1mmHg 13 cheap kamagra super 160mg overnight delivery. Because the pressure throughout the fluid is the same purchase kamagra super amex, the force F2 acting on the area A2 in Fig cheap 160 mg kamagra super fast delivery. There are order kamagra super without a prescription, however, soft-bodied animals (such as the sea anemone and the earthworm) that lack a firm skeleton. For the purpose of understanding the movements of an animal such as a worm, we can think of the animal as consisting of a closed elastic cylinder filled with a liquid; the cylinder is its hydrostatic skeleton. The worm pro- duces its movements with the longitudinal and circular muscles running along the walls of the cylinder (see Fig. Because the volume of the liquid in the cylinder is constant, contraction of the circular muscles makes the worm thinner and longer. Contraction of the longitudinal muscles causes the animal to become shorter and fatter. If the longitudinal muscles contract only on one side, the animal bends toward the contracting side. By anchoring alternate ends of its body to a surface and by producing sequential longitudinal and cir- cular contractions, the animal moves itself forward or backward. Assume that the circular muscles running around its circumference are uniformly distributed along the length of the worm and that the effective area of the muscle per unit length of the worm Section 7. The force Ff in the forward direction generated by this pressure, which stretches the worm, is 2 4 Ff P × πr 1. We will now use Archimedes’ principle to calculate the power required to remain afloat in water and to study the buoyancy of fish. If its density is greater than that of water, the animal must perform work in order not to sink. We will calculate the power P required for an animal of volume V and density ρ to float with a fraction f of its volume submerged. This problem is similar to the hovering flight we discussed in Chapter 6, but our approach to the problem will be different. This motion accelerates the water downward and results in the upward reaction force that supports the animal. If the area of the moving limbs is A and the final velocity of the accelerated water is v, the mass of water accelerated per unit time in the treading motion is given by (see Exercise 7-1) m Avρw (7. The force producing this change in the momentum is applied to the water by the moving limbs. The kinetic energy given to the water each second is half the product of the mass accelerated each second and the squared final velocity of the water. Note that, in our calculation, we have neglected the kinetic energy of the moving limbs. We can find the percentage of the body volume X occupied by the porous bone that makes the average density of the fish be the same as the density of sea water (1. In fish that possess swim bladders, the decrease in density is provided by the gas in the bladder. Because the density of the gas is negligible compared to the density of tissue, the volume of the swim bladder required to reduce the density of the fish is smaller than that of the porous bone. For exam- ple, to achieve the density reduction calculated in the preceding example, the volume of the bladder is only about 4% of the total volume of the fish (see Exercise 7-6). The cuttlefish alters its density by injecting or withdrawing fluid from its porous bone. Fish with swim bladders alter their density by changing the amount of gas in the bladder. A molecule in the interior of the liquid is surrounded by an equal number of neighboring molecules in all directions. Therefore, the net resultant inter- molecular force on an interior molecule is zero. Because there are no molecules above the surface, a molecule here is pulled predominantly in one direction, toward the interior of the surface. This causes the surface of a liquid to con- tract and behave somewhat like a stretched membrane. This contracting ten- dency results in a surface tension that resists an increase in the free surface of the liquid. It can be shown (see reference [7-7]) that surface tension is a force acting tangential to the surface, normal to a line of unit length on the surface (Fig. At the same time, however, these molecules are also subject to the attractive cohesive force exerted by the liquid, which pulls the molecules in the opposite direction. If the adhesive force is greater than the cohesive force, the liquid wets the container wall, and the liquid surface near the wall is curved upward. If the adhesion is greater than the cohesion, a liquid in a narrow tube will rise to a specific height h (see Fig. Another consequence of surface tension is the tendency of liquid to assume a spherical shape. Such an uncontained liquid forms into a sphere that can be noted in the shape of raindrops. The pressure inside the spherical liquid drop is 92 Chapter 7 Fluids higher than the pressure outside. In other words, to create gas bubble of radius R in a liquid with surface tension T, the pressure of the gas injected into the liquid must be greater than the pressure of the surrounding liquid by P as given in Eq. As will be shown in the following sections, the effects of surface tension are evident in many areas relevant to the life sciences. These spaces act as capillaries and in part govern the motion of water through the soil. When water enters soil, it penetrates the spaces between the small particles and adheres to them. If the water did not adhere to the particles, it would run rapidly through the soil until it reached solid rock. Because of adhesion and the resulting capillary action, a significant fraction of the water that enters the soil is retained by it. For a plant to withdraw this water, the roots must apply a negative pressure, or suction, to the moist soil. For example, if the effective capillary radius of the soil is 10−3 cm, the pressure required to withdraw the water is 1. Because capillary action is inversely proportional to the diameter of the capillary, finely grained soil will hold water more tightly than soil of similar material with larger grains (see Fig. When all the pores of the soil are filled with water, the surface mois- ture tension is at its lowest value. In other words, under these conditions the required suction pressure produced by the plant roots to withdraw the water from the soil is the lowest. As the soil loses moisture, the remaining water tends to be bound into the narrower capillaries. In addition, as the moisture content decreases, sec- tions of water become isolated and tend to form droplets. If, for example, the radius of a droplet decreases to 10−5 cm, the pressure required to draw the water out of the droplet is about 14. Capillary action also depends on the strength of adhesion, which in turn depends on the material composition of the capillary surface. There is a limit to the pressure that roots can produce in order to withdraw water from the soil. A plant may thrive in loam and yet wilt in a clayey soil with twice the moisture content. Many of these insects are adapted to utilize the surface tension of water for locomotion. The surface tension of water makes it possible for some insects to stand on water and remain dry. As is shown in Exercise 7-11, a 70 kg person would have to stand on a platform about 10 km in perimeter to be supported solely by surface tension.

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