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Introduction

Introduction With the onset of 2000, the average North Americans life span has been extended by three years. The predictable consequences are detrimental changes in body composition, including loss of lean body mass, strength, flexibility, and bone density, along with the increase in body weight and body fat. Inactivity with aging is the primary factor in these changes, because physical activity levels are one of the most important factors affecting body composition from childhood through old age. (Adams, K., OShea, P., & OShea, K. 1999) Our knowledge of the affects of aging on fatigability, endurance, the ability to maintain force and power output is limited, and the few studies that have been performed are inconclusive. It is therefore important to assess these areas to give a more detailed account of muscle fatigue, endurance, and contractibility of aging humans. The results of the studies could prove beneficial in helping to prepare older humans to overcome and enhance his or her ability to live an independent lifestyle.

With advancing age, muscle volume is reduced, and the aging atrophy, referred to as “sarcopenia” is accompanied by a decrease in muscle strength. The reduction in muscle strength seems to be equal for both sexes, but women are generally weaker than men throughout all ages. (Lindstrom, B., Lexell, J., Gerdle, B., & Downham, D. 1997) Since gait pattern also changes with age, especially in women, older individuals have an increased risk of falls and hip fractures. However, both arm and leg muscles in aging men and women can adapt successfully to increased use, in particular following periods of heavy resistance training. Physical exercise is therefore, considered beneficial in reducing the risk of muscle atrophy among older humans. (Linstrom, et al., 1997) It has been suggested that once strength declines below certain threshold levels required for activities of daily living, significant functional impairment begins to happen.

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Along with a change in strength is a change in muscle contractile properties, the peak evoked twitch torque may decline and contractile speed becomes typically slowed in aging humans (Hicks, A. L. & McCartney, N. 1996). The slowing is indicated by prolonged contraction and relaxation times during stimulated contractions. One reason for slowing is thought to be a loss of motor units leading to a loss of type II muscle fibers and a shift toward a slower muscle fiber type.

It has been suggested that the slowing of contractile muscle with age can result in a fusion of muscle force at lower motor unit firing rate. Such early ending of force may cause force to be produced at lower frequency of stimulation, this has been speculated to be advantageous during voluntary contraction, resulting in an increase in neural efficiency or a decreased motor drive necessary to produce desired force (Ng, A. V. & Kent-Braun, J. A., 1999). Anatomy & Physiology The study by Hicks and McCartney (1996) purpose was to compare the isometric contractile characteristics and fatigability in the elbow flexors and ankle dorsi flexors in older males and females to determine the affects of almost two years, twice per week weightlifting training.

The elbow flexors consist of the biceps brachii, pronator teres (weak flexor), and flexor carpi radialis (synergist); the nerve supply is the median nerve. The Biceps brachii is a two-headed fusiform muscle; the bellies unite as it reaches the insertion point, the tendon of the long head helps to stabilize the shoulder joint. The biceps brachii flexes elbow joint and supinates the forearm; these actions usually occur at the same time (ex. When you open a bottle of wine, it turns the corkscrew and pulls the cork). The Pronator teres is a two-headed muscle that can be seen in superficial view between the proximal margins of brachioradialis and the flexor carpi radialis. This muscle pronates the forearm and is a weak flexor of the elbow. The Flexor carpi radialis runs diagonally across the forearm; midway its fleshy belly is replaced by a flat tendon that becomes cordlike at the wrist; it is a powerful flexor of the wrist, it abducts the hand and is a synergist of elbow flexion.

The ankle dorsi flexor muscles consist of the tibialis anterior, extensor digitorum longus, peroneus tertius, and the extensor hallucis longus the nerve supply is the deep peroneal nerve. The Tibialis anterior muscle is superficial of the anterior leg, laterally it parallels the sharp anterior margin of the tibia. The tibialis anterior is the prime mover of dorsi flexion; it also inverts the foot and assists in supporting the medial longitudinal arch of the foot. The Extensor digitorum longus (EDL) is on the anterolateral surface of the leg, lateral to the tibialis anterior muscle. The EDL dorsi flexes the foot and is the prime mover of toe extension. The Peroneus tertius is a small muscle that is usually continuous and fused with the distal part of the extensor digitorum longus. It dorsi flexes and everts the foot.

The Extensor hallucis is deep to the extensor digitorum longus and tibialis anterior it extends the great toe and dorsi flexes the foot. The study done by Lexell, et al. (1997) focused on the fatigue rate, endurance level and the relative reduction in muscle force during maximal voluntary contraction (MVC) while performing dynamic knee extensions. The knee extensors measured were the rectus femoris, vastus lateralis, vastus medialis, vastus intermedius (quadriceps), and the triceps surae. The rectus femoris is a superficial muscle of the anterior thigh it runs straight down the thigh and is the only one of the quadriceps to cross the hip joint. It extends the knee and flexes the thigh at the hip.

The nerve supply is the femoral nerve. The vastus lateralis forms the lateral aspect of the thigh and extends the knee. The vastus medialis forms the inferomedial aspect of the thigh, it extends the knee and its inferior fibers stabilize the patella. The vastus intermedius is obscured by the rectus femoris, and lies between the vastus lateralis and vastus medialis on the anterior of the thigh. Like the above muscles it extends the knee and its nerve supply is the femoral nerve. This group, along with the rectus femoris, forms the quadriceps.

The Triceps surae refers to the muscle pair that shapes the posterior calf and inserts by a common tendon into the calcaneus of the heel (Gastrocnemius and soleus). Research Review Skeletal Muscle Fatigue and Endurance in Young and Old Men and Women Britta Lindstrom, Jan Lexell, Bjorn Gerdle, and David Downham Lindstrom et al (1997) used 38 physically healthy individuals, 22 young and 16 old to test the fatigue rate, the endurance level, and the relative reduction in muscle force. There were 14 men and 8 women 28 years old that made up the young group. The older group consisted of 8 men and women 73 years old. None of the 38 volunteers were elite athletes, but all of them participated regularly I low intensity aerobic exercise (walking, cycling, etc.).

(Lindstrom et al.1997) The term fatigue is defined as failure to maintain force or power output, in contrast to weakness, which is failure to generate force. The method used to assess muscle fatigue has been used for over 10 years and measured the reduction in muscle force during 100 200 repeated contractions. It also allows the researchers to estimate indirectly the maximal voluntary contraction and to determine muscle endurance. (Lindstrom et al.1997) In this study, muscle fatigue and endurance were assessed in the knee exten …

Introduction

Introduction ————————————————– —————————— Sather is an object oriented language designed to be simple, efficient, safe, and non-proprietary. It aims to meet the needs of modern research groups and to foster the development of a large, freely available, high-quality library of efficient well-written classes for a wide variety of computational tasks. It was originally based on Eiffel but now incorporates ideas and approaches from several languages. One way of placing it in the ‘space of languages’ is to say that it attempts to be as efficient as C, C++, or Fortran, as elegant but safer than Eiffel or CLU, and to support higher-order functions as well as Common Lisp, Scheme, or Smalltalk. Sather has garbage collection, statically-checked strong (contravariant) typing, multiple inheritance, separate implementation and type inheritance, parameterized classes, dynamic dispatch, iteration abstraction, higher-order routines and iters, exception handling, assertions, preconditions, postconditions, and class invariants.

Sather code can be compiled into C code and can efficiently link with object files of other languages. pSather, the parallel and distributed extension, presents a shared memory abstraction to the programmer while allowing explicit placement of data and threads. Sather and the ICSI Sather compiler have a very unrestrictive license aimed at encouraging contribution to the public library without precluding the use of Sather for proprietary projects. This chapter will provide a basic introduction for new users, pointing to sources of information about the language and the compiler. It also contains a summary of Sather features – for those familiar with another object-oriented language, this section provides an overview of the key features of Sather. 1.1 Acknowledgements This text has its roots in the Sather 1.1 specification, the Eclectic tutorial and Holger’s iterator tutorial.

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This document also contains several organizational ideas and some text from S. Omohundro’s originally planned Sather book. This text has benefitted from corrections, comments and suggestions from several people including Cary D. Renzema, Jerome Feldman, Claudio Fleiner and Arno Jacobsen. Particular thanks to Cary, Arno and Feldman for detailed error reports. Arno also made several suggestions regarding terminology and examples that have been incorporated.

1.2 How to read this Document This document is meant to be a complete description of Sather 1.1, and is intended as an introduction to the language for a person with some programming background. It is more expository in nature than the specification and contains sections that motivate particular aspects of the language, such as the overloading rules. In addition, it deals with some more abstract design issues that arise when programming in Sather (such as the effect of the contra-variant subtyping rule). 1.3 Sources of Information This section briefly introduces some concepts important to Sather that the reader may not have been exposed to in C++ [2]. It isn’t meant as a complete language tutorial.

More information of a tutorial nature is available from the WWW page: http://www.icsi.berkeley.edu/Sather At the time of this writing, the only compiler implementing the 1.1 language specification is available from ICSI. It is freely available, includes source for class libraries and the compiler, and compiles into ANSI C. This compiler has been ported to a wide range of UNIX and PC operating systems. 1.4 Obtaining the Compiler The ICSI Sather 1.1 compiler can be obtained by anonymous ftp at ftp.icsi.berkeley.edu: /pub/sather Other sites also mirror the Sather distribution. The distribution includes installation instructions, ‘man’ pages, the standard libraries and source for the compiler (in Sather).

Documentation, tutorials and up-to-date information are also available at the Sather WWW page: http://www.icsi.berkeley.edu/~sather ICSI also maintains a library of contributed Sather code at this page. There is a newsgroup devoted to Sather: comp.lang.sather There is also a Sather mailing list if you wish to be informed of Sather releases; to subscribe, send email to: sather- It is not necessary to be on the mailing list if you read the Sather newsgroup. 1.4.1 How do I ask questions? If it appears to be a problem that others would have encountered (on platform ‘X’, I tried to install it but the it failed to link with the error ‘Y’), then the newsgroup is a good place to ask. If you have problems with the compiler or questions that are not of general interest, mail to one of sather- psather- This is also where you want to send bug reports. 1.5 Summary of Features This section provides a summary of Sather’s features, with particular attention to features that are not found in the most common object oriented languages.

1.5.1 Basic Concepts Data structures in Sather are constructed from objects, each of which has a specific concrete type that determines the operations that may be performed on it. Abstract types specify a set of operations without providing an implementation and correspond to sets of concrete types. The implementation of concrete types is defined by textual units called classes; abstract types are specified by textual units called abstract classes. Sather programs consist of classes and abstract class specifications. Each Sather variable has a declared type which determines the types of objects it may hold.

Classes define the following features: attributes which make up the internal state of objects, shareds and constants which are shared by all objects of a type, and methods which may be either routines or iterators. Any features are by default public, but may be declared private to allow only the class in which it appears access to it. An attribute or shared may instead be declared readonly to allow only the class in which it appears to modify it. Accessor routines are automatically defined for reading or writing attributes, shareds, and constants. The set of non-private methods in a class defines the interface of the corresponding type.

Method definitions consist of statements; for their construction expressions are used. There are special literal expressions for boolean, character, string, integer, and floating point objects. Certain conditions are described as fatal errors. These conditions should never occur in correct programs and all implementations of Sather must be able to detect them. For efficiency reasons, however, implementations may provide the option of disabling checking for certain conditions.

1.5.2 Garbage Collection and Checking Like many object-oriented languages, Sather is garbage collected, so programmers never have to free memory explicitly. The runtime system does this automatically when it is safe to do so. Idiomatic Sather applications generate far less garbage than typical Smalltalk or Lisp programs, so the cost of collecting tends to be lower. Sather does allow the programmer to manually deallocate objects, letting the garbage collector handle the remainder. With checking compiled in, the system will catch dangling references from manual deallocation before any harm can be done. More generally, when checking options have been turned on by compiler flags, the resulting program cannot crash disastrously or mysteriously. All sources of errors that cause crashes are either eliminated at compile-time or funneled into a few situations (such as accessing beyond array bounds) that are found at run-time precisely at the source of the error. 1.5.3 No Implicit Calls Sather does as little as possible behind the user’s back at runtime.

There are no implicitly constructed temporary objects, and therefore no rules to learn or circumvent. This extends to class constructors: all calls that can construct an object are explicitly written by the programmer. In Sather, constructors are ordinary routines distinguished only by a convenient but optional calling syntax (page 107). With garbage collection there is no need for destructors; however, explicit finalization is available when desired (page 143). Sather never converts types implicitly, such as from integer to character, integer to floating point, single to double precision, or subclass to superclass. With neither implicit construction nor conversion, Sather resolves routine overloading (choosing one of several similarly named operations based on argument types) much more clearly than C++.

The programmer can easily deduce which routine will be called (page 47). In Sather, the redefinition of operators is orthogonal to the rest of the language. There is ”syntactic sugar” (page 116) for standard infix mathematical symbols such as ‘+’ and ‘^’ as calls to otherwise ordinary routines with names ‘plus’ and ‘pow’. ‘a+b’ is just another way of writing ‘a.plus(b)’. Similarly, ‘a[i]’ translates to ‘a.aget(i)’ when used in an expression. An assignment ‘a[i] := expr’ translates into ‘a.aset(i,expr)’.

1.5.4 Separation of Subtyping and Code Inclusion In many object-oriented languages, the term ‘inheritance’ is used to mean two things simultaneously. One is subtyping, which is the requirement that a class provide implementations for the abstract methods in a supertype. The other is code inheritance (called code inclusion in Sather parlance) which allows a class to reuse a portion of the implementation of another class. In many languages it is not possible to include code without subtyping or vice versa. Sather provides separate mechanisms for these two concepts.

Abstract classes represent interfaces: sets of signatures that subtypes of the abstract class must provide. Other kinds of classes provide implementation. Classes may include implementation from other classes using a special ‘include’ clause; this does not affect the subtyping relationship between classes. Separating these two concepts simplifies the language considerably and makes it easier to understand code. Because it is only possible to subtype from abstract classes, and abstract classes only specify an interface without code, sometimes in Sather one factors what would be a single class in C++ into two classes: an abstract class specifying the interface and a code class specifying code to be included. This often leads to cleaner designs. Issues surrounding the decision to explicitly separate subtyping and code inclusion in Sather are discussed in the ICSI technical report TR 93-064: ”Engineering a Programming Language: The Type and Class System of Sather,” also published as [7].

It is available at the Sather WWW page. 1.5.5 Iterators Early versions of Sather used a conventional ‘until..loop..end’ statement much like other languages. This made Sather susceptible to bugs that afflict looping constructs. Code which controls loop iteration is known for tricky ”fencepost errors” (incorrect initialization or termination). Traditional iteration constructs also require the internal implementation details of data structures to be exposed when iterating over their elements.

Simple looping constructs are more powerful when combined with heavy use of cursor objects (sometimes called ‘iterators’ in other languages, although Sather uses that term for something else entirely) to iterate through the contents of container objects. Cursor objects can be found in most C++ libraries, and they allow useful iteration abstraction. However, they have a number of problems. They must be explicitly initialized, incremented, and tested in the loop. Cursor objects require maintaining a parallel cursor object hierarchy alongside each container class hierarchy. Since creation is explicit, cursors aren’t elegant for describing nested or recursive control structures.

They can also prevent a number of important optimizations in inner loops. An important language improvement in Sather 1.0 over earlier versions was the addition of iterators. Iterators are methods that encapsulate user defined looping control structures just as routines do for algorithms. Code using iterators is more concise, yet more readable than code using the cursor objects needed in C++. It is also safer, because the creation, increment, and termination check are bound together inviolably at one point. Each class may define many sorts of iterators, whereas a traditional approach requires a different yet intimately coupled class for each kind of iteration over the major class.

Sather iterators are part of the class interface just like routines. Iterators act as a lingua-franca for operating on collections of items. Matrices define iterators to yield rows and columns; tree classes have recursive iters to traverse the nodes in pre-order, in-order, and post-order; graph classes have iters to traverse vertices or edges breadth-first and depth-first. Other container classes such as hash tables, queues, etc. all provide iters to yield and sometimes to set elements.

Arbitrary iterators may be used together in loops with other code. The rationale of the Sather iterator construct and comparisons with related constructs in other languages can be found in the ICSI technical report TR 93-045: ”Sather Iters: Object-Oriented Iteration Abstraction,” also published as [5]. It is available at the Sather WWW page. 1.5.6 Closures Sather provides higher-order functions through method closures, which are similar to closures and function pointers in other languages. These allow binding some or all arguments to arbitrary routines and iterators but defer the remaining arguments and execution until a later time.

They support writing code in an applicative style, although iterat …

Introduction:

A. Have you ever experienced the unconditional love of a cat or dog?
Have you ever buried your face in a pet’s soft fur—and for a
delightful moment or two —- felt a moment of peace and
tranquility? Many people have.

B. But the value of a pet extends well beyond moments like these. A
pet may actually help keep you healthy.

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C. If you do not already have a pet, you may consider adopting one.

If you already have a pet, you may cherish that pet more after
what I have to say.

Body:
A. What scientists know about your health and pets.

1. Dogs need to be walked. The benefits of walking are well
documented.

2. Protect your health after a heart attack. People who own
pets compared to those who do not, are more likely to be
alive a tear after a heart attack.

3. Protect your heart blood vessels and help you cope with
stress. People who have pets versus those who don’t have
lower heart rates and blood pressure. People with pets have
a less increase in heart rate and blood pressure when put
under stress. Their blood pressure also dropped faster after
a stressful event. People with pets show lower cholesterol.

4. Improve your mood and sense of well being. Studies show that
adults who have pets are less likely to experience depression
than their counterparts who didn’t have pets. In people with
AIDS, those who have pets experienced less depression than
did the people with AIDS who didn’t have pets. People in
nursing homes also experience less depression.

5. General pet owners both younger and older have fewer overall
health complaints. They have less problems sleeping, fewer
aches and pains, fewer headaches, and less digestion
problems.

B. Pets and emotional well being.

1. Petting a pet gives some people a sense of purpose, and
encourages older people to be less apathetic and more
involved in daily activities.

2. A pet gives a support system in times of crisis. If someone
has experienced a loss of a loved one, a pet may be just the
distraction they need.

3. Studies show that children with pets can teach
responsibility. It helps build self esteem and self-
confidence. Pets offer exposure to important issues such as
reproduction, birth, illness, accidents, death, and grief.

Pets provide a connection to nature and teach respect,
empathy, and patience for other living things. Pets also
offer unconditional love, loyalty, affection, and comfort.

4. Pets cannot replace human relationships, but they certainly
can enhance them.

C. Pets have been attributed to alerting owners of various
Hazards like fire and intruders. Not to rely on, but not
something to be overlooked.

D. Before getting a pet, there are some things to consider.

1. Do you have time for a pet? Many pets such as cats and dogs
need daily exercise and your companionship. Pets generally
live up to 20 years.

2. Are you prepared for the financial commitment? Beyond the
cost of food, you’ll have the cost of veterinary care,
licenses and grooming. Be prepared for unanticipated costs,
such as replacement cost for damaged property.

3. Are pets allowed where you live? If you are in an apartment
this is an important issue. If you plan on moving in the
future where pets are not allowed consider what will happen
to your pet.

4. Do you have proper living space? If you are thinking of
bringing home a dog, will you have adequate space to
accommodate for your pet’s activity level? Some breeds are
more active than others. You may need a yard for your pet to
burn off that energy. If you live in an apartment, consider
a breed whose barking is not so loud or frequent as to
disturb the neighbors.

5. Are you physically capable of taking care of a pet? Consider
whether you or others in your home have a history of
allergies. If you have physical limitations, be sure that it
won’t keep you from caring for your pet.

6. Do your research so you can pick a pet most suitable to your
personality and lifestyle.

Conclusion:
The companionship and unconditional love a pet provides is priceless.

Although time-consuming, the relationship can benefit you and your pet.

The care and nurturing you provide can result in improved health and well
being.

x

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I'm Abigail

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