Astrophysics & Astronomy

Astrophysics & Astronomy

Agrophysics

Agrophysics is a branch of science bordering on agronomy and physics, whose objects of study are the agroecosystem - the biological objects, biotope and biocoenosis affected by human activity, studied and described using the methods of physical sciences.

Agrophysics is closely related to biophysics, but is restricted to the biology of the plants, animals, soil and an atmosphere involved in agricultural activities and biodiversity. It is different from biophysics in having the necessity of taking into account the specific features of biotope and biocoenosis, which involves the knowledge of nutritional science and agroecology, agricultural technology, biotechnology, genetics etc.

Principles of physical sciences

Agrophysics is close to certain fundamental sciences like biology, whose methods and knowledge it utilizes (especially in the field of environmental ecology and plant physiology), and physics, from which it acquires the research methods, especially that of physical experiment and model.

The scope of interest of agrophysics is not focused solely on technical problems from agronomy and on practical implementation of sciences and that are aspects that makes it different from agricultural engineering which provides grounds for classifying agrophysics as the fundamental sciences.

Physical models, closely related to biophysics, are ready to solve either global or local aspects of behaviour of the complex ecosystems to be studied, including of energy consumption, food safety

etc....

Principles of history

The needs of agriculture, concerning the past experience study of the local complex soil and next plant-atmosphere systems, lay at the root of the emergnece of new branch - agrophysics dealing this with experimental physics. The scope of the branch starting from soil science (physics) and originally limited to the study of relations within the soil environment, expanded over time onto influencing the properties of agricultural crops and produce as foods and raw postharvest materials, and onto the issues of quality, safety and labeling concerns, considered distinct from the field of nutrition for application in food science.

A research centre that is focused on the development of the Science is the Institute of Agrophysics, Polish Academy of Sciences in Lublin. cyt: "Agrophysics, utilizing the achievements of Exact Sciences for solving major problems of Agriculture, is involved in study of materials and processes occurring in the production and processing of agricultural crops, with particular emphasis on the condition of the environment and the quality of farming materials and food productions."

See also

• Agriculture
• Agroecology
• Genomics
• Metagenomics
• Metabolomics
• Nitrogenomics
• Physics (Aristotle)
• Proteomics
• Soil plant atmosphere continuum

References

• Encyclopedia of Agrophysics in series: Encyclopedia of Earth Sciences Series edts. Jan Glinski, Jozef Horabik, Jerzy Lipiec, 2011, Publisher: Springer, ISBN 978-90-481-3585-1

Biophysics

The majority of graduates in the Biophysics program have been undergraduate majors in physics or physical chemistry, although others have come from areas such as biology and electrical engineering. Consequently, the course requirements for admission are somewhat elastic, with a focus on more quantitative areas. The degree program is designed to be completed in a maximum of six years. The program is highly flexible, and special effort has been devoted to minimizing formal requirements.

The first part of the program seeks to introduce the students directly to the faculty members and their research, enabling the student to make a considered choice of research advisor, and to involve the student in the diverse areas of biophysics through laboratory as well as course work. The first year's training in the Biophysics Program provides an introduction to five diverse areas of Biophysics:

1. Structural Molecular Biology
2. Cell and Membrane Biophysics
3. Molecular Genetics
4. Physical Biochemistry
5. Neuroscience

Biophysics, Introduction to Laboratory Research, brings professors from all over the University for one-hour seminars on their specific areas of research interest, allowing the students a period of time to familiarize themselves with research opportunities at their first laboratory rotation later in the first semester.

First Year:

Several rotations as well as course work are completed in the year to year-and-a-half of study. A year's work for a resident student normally consists of four courses (eight half-courses) of advanced grade.

Second Year:

Students continue with course work and laboratory rotations.

A semester of teaching is required in the second year.
Students chose their research advisor by the end of their second year.
Preliminary Qualifying examination must be completed by the end of the second year. Student must pass this exam before beginning thesis research.

Third Year and beyond:
Student meets at least annually with his or her Dissertation Advisory Committee (DAC).
Student engages in a period of intensive research culminating in publications and the receiving of the Ph.D. degree.

Areas of concentration and suggested course work is as follows:

* Structural Molecular Biology
o Genomics and Computational Biology
o Structure and Function of Proteins and Nucleic Acids
o Structural Biology of the Flow of Information in the Cell
o Crystal Symmetry, Diffraction, and Structure Analysis
o Chemical Biology
o Molecular Structure and Function
o Molecular Biology
o Proteins: Structure, Function and Catalysis
o Macromolecular NMR

* Molecular Genetics
o Molecular Genetics of Neural Development and Behavior
o Developmental Genetics and Genomics
o Molecular Mechanisms of Gene Control
o Principles of Genetics

* Physical Biochemistry
o Physical Chemistry
o Frontiers in Biophysics
o Molecular Biophysics and Biophysical Chemistry
o Topics in Biophysics
o Quantum Mechanics I
o Single-molecule Biophysics

* Cell and Membrane Biophysics
o Molecular and Cellular Immunology
o Biochemistry of Membranes
o Molecular Biology of the Cell
o Growth Factors and Signal Transduction

* Mathematical Biophysics
o Methods of Analysis and Applications
o Introduction to Systems Analysis with Physiological Applications
o Signals and Systems
o Nonlinear Dynamical Systems
o Population Genetics
o Population and Community Ecology
o Complex and Fourier Analysis
o Ordinary and Partial Differential Equations
o Mathematical Modeling
o Physical Mathematics I, II
o Fundamentals of Computational Biology
o Mathematics in Biology

* Neurosciences
o Systems Neuroscience
o Cellular Basis of Neuronal Function
o Experimental Neuroscience
o Molecular and Developmental Neurobiology
o Neural Signal Processing
o Introduction to Neurobiology
o Neurophysiology of Central Circuits
o Molecular Neurobiology

Biophysics is an interdisciplinary science that uses the methods of physical science to study biological systems.^[1] Studies included under the branches of biophysics span all levels of biological organization, from the molecular scale to whole organisms and ecosystems. Biophysical research shares significant overlap with biochemistry, nanotechnology, bioengineering, agrophysics and systems biology.

Molecular biophysics typically addresses biological questions that are similar to those in biochemistry and molecular biology, but the questions are approached quantitatively. Scientists in this field conduct research concerned with understanding the interactions between the various systems of a cell, including the interactions between DNA, RNA and protein biosynthesis, as well as how these interactions are regulated. A great variety of techniques are used to answer these questions.

Fluorescent imaging techniques, as well as electron microscopy, x-ray crystallography, NMR spectroscopy and atomic force microscopy (AFM) are often used to visualize structures of biological significance. Conformational change in structure can be measured using techniques such as dual polarisation interferometry and circular dichroism. Direct manipulation of molecules using optical tweezers or AFM can also be used to monitor biological events where forces and distances are at the nanoscale. Molecular biophysicists often consider complex biological events as systems of interacting units which can be understood through statistical mechanics, thermodynamics and chemical kinetics. By drawing knowledge and experimental techniques from a wide variety of disciplines, biophysicists are often able to directly observe, model or even manipulate the structures and interactions of individual molecules or complexes of molecules.

In addition to traditional (i.e. molecular and cellular) biophysical topics like structural biology or enzyme kinetics, modern biophysics encompasses an extraordinarily broad range of research, from bioelectronics to quantum biology involving both experimental and theoretical tools. It is becoming increasingly common for biophysicists to apply the models and experimental techniques derived from physics, as well as mathematics and statistics (see biomathematics), to larger systems such as tissues, organs, populations and ecosystems.

Focus as a subfield

Biophysics often does not have university-level departments of its own, but has presence as groups across departments within the fields of molecular biology, biochemistry, chemistry, computer science, mathematics, medicine, pharmacology, physiology, physics, and neuroscience. What follows is a list of examples of how each department applies its efforts toward the study of biophysics. This list is hardly all inclusive. Nor does each subject of study belong exclusively to any particular department. Each academic institution makes its own rules and there is much overlap between departments.

• Biology and molecular biology - Almost all forms of biophysics efforts are included in some biology department somewhere. To include some: gene regulation, single protein dynamics, bioenergetics, patch clamping, biomechanics.
• Structural biology - Ångstrom-resolution structures of proteins, nucleic acids, lipids, carbohydrates, and complexes thereof.
• Biochemistry and chemistry - biomolecular structure, siRNA, nucleic acid structure, structure-activity relationships.
• Computer science - Neural networks, biomolecular and drug databases.
• Computational chemistry - molecular dynamics simulation, molecular docking, quantum chemistry
• Bioinformatics - sequence alignment, structural alignment, protein structure prediction
• Mathematics - graph/network theory, population modeling, dynamical systems, phylogenetics.
• Medicine and neuroscience - tackling neural networks experimentally (brain slicing) as well as theoretically (computer models), membrane permitivity, gene therapy, understanding tumors.
• Pharmacology and physiology - channel biology, biomolecular interactions, cellular membranes, polyketides.
• Physics - biomolecular free energy, stochastic processes, covering dynamics.
• Quantum biophysics involves quantum information processing of coherent states, entanglement between coherent protons and transcriptase components, and replication of decohered isomers to yield time-dependent base substitutions. These studies imply applications in quantum computing.
• Agronomy and agriculture

Many biophysical techniques are unique to this field. Research efforts in biophysics are often initiated by scientists who were traditional physicists, chemists, and biologists by training.

Fields and areas of research

Fields and areas of research

Accelerator physics Acoustics Agrophysics Analog Electronics Force microscopy and imaging Ballistics Biophysics Communication Physics Computational physics Control Theory Digital Electronics Econophysics Engineering physics Fiber Optics Fluid dynamics Geophysics Laser physics Medical physics

Metrological Physics Microfluidics Nanotechnology Nondestructive testing Nuclear engineering Nuclear technology Optics Optoelectronics Photovoltaics Plasma physics Quantum electronics Semiconductor physics and devices Soil Physics Solid state physics Space physics Spintronics Superconductors Vehicle dynamics

Analogue electronics

Analogue electronics (or analog in American English) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two different levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represents the signal. The word analogue is derived from the Greek word ανάλογος (analogos) meaning "proportional".^[1]

An analogue signal uses some attribute of the medium to convey the signal's information. For example, an aneroid barometer uses the angular position of a needle as the signal to convey the information of changes in atmospheric pressure.^[2]Electrical signals may represent information by changing their voltage, current, frequency, or total charge. Information is converted from some other physical form (such as sound, light, temperature, pressure, position) to an electrical signal by a transducer which converts one type of energy into another (e.g. a microphone).^[3]

The signals take any value from a given range, and each unique signal value represents different information. Any change in the signal is meaningful, and each level of the signal represents a different level of the phenomenon that it represents. For example, suppose the signal is being used to represent temperature, with one volt representing one degree Celsius. In such a system 10 volts would represent 10 degrees, and 10.1 volts would represent 10.1 degrees.

Another method of conveying an analogue signal is to use modulation. In this, some base carrier signal has one of its properties altered: amplitude modulation (AM) involves altering the amplitude of a sinusoidal voltage waveform by the source information, frequency modulation (FM) changes the frequency. Other techniques, such as phase modulation^[4] or changing the phase of the carrier signal, are also used.

In an analogue sound recording, the variation in pressure of a sound striking a microphone creates a corresponding variation in the current passing through it or voltage across it. An increase in the volume of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same waveform or shape.

Mechanical, pneumatic, hydraulic and other systems may also use analogue signals.

Inherent noise

Analogue systems invariably include noise; that is, random disturbances or variations, some caused by the random thermal vibrations of atomic particles. Since all variations of an analogue signal are significant, any disturbance is equivalent to a change in the original signal and so appears as noise.^[5] As the signal is copied and re-copied, or transmitted over long distances, these random variations become more significant and lead to signal degradation. Other sources of noise may include external electrical signals or poorly designed components. These disturbances are reduced by shielding, and using low-noise amplifiers (LNA).^[6]

Analogue vs. digital electronics

Since the information is encoded differently in analogue and digital electronics, the way they process a signal is consequently different. All operations that can be performed on an analogue signal such as amplification, filtering, limiting, and others, can also be duplicated in the digital domain. Every digital circuit is also an analogue circuit, in that the behaviour of any digital circuit can be explained using the rules of analogue circuits.

The first electronic devices invented and mass produced were analogue. The use of microelectronics has reduced the cost of digital techniques and now makes digital methods feasible and cost-effective such as in the field of human-machine communication by voice.^[7]

The main differences between analogue and digital electronics are listed below:

Noise

Because of the way information is encoded in analogue circuits, they are much more susceptible to noise than digital circuits, since a small change in the signal can represent a significant change in the information present in the signal and can cause the information present to be lost. Since digital signals take on one of only two different values, a disturbance would have to be about one-half the magnitude of the digital signal to cause an error; this property of digital circuits can be exploited to make signal processing noise-resistant. In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. Digital circuits use this principle to regenerate the signal at each logic gate, lessening or removing noise.^[8]

Precision

A number of factors affect how precise a signal is, mainly the noise present in the original signal and the noise added by processing. See signal-to-noise ratio. Fundamental physical limits such as the shot noise in components limits the resolution of analogue signals. In digital electronics additional precision is obtained by using additional digits to represent the signal; the practical limit in the number of digits is determined by the performance of the analogue-to-digital converter (ADC), since digital operations can usually be performed without loss of precision. The ADC takes an analogue signal and changes into a series of binary numbers. The ADC may be used in simple digital display devices e. g. thermometers, light meters but it may also be used in digital sound recording and in data acquisition. However, a digital-to-analogue converter (DAC) is used to change a digital signal to an analogue signal. A DAC takes a series of binary numbers and converts it to an analogue signal. It is common to find a DAC in the gain-control system of an op-amp which in turn may be used to control digital amplifiers and filters.^[9]

Design difficulty

Analogue circuits are harder to design, requiring more skill, than comparable digital systems.^{[citation needed]} This is one of the main reasons why digital systems have become more common than analogue devices. An analogue circuit must be designed by hand, and the process is much less automated than for digital systems. However, if a digital electronic device is to interact with the real world, it will always need an analogue interface.^[10] For example, every digital radio receiver has an analogue preamplifier as the first stage in the receive chain.

See also

• Analogue computer
• Analogue signal
• Digital - See here for a discussion of digital vs. analogue.
• Analogue recording vs. digital recording
• Analogue chip
• Analogue verification

References

1. ^ Concise Oxford dictionary (10 ed.). Oxford University Press Inc.. 1999. ISBN 0198602871.

2. ^ Plympton, George Washington (1884). The aneroid barometer: its construction and use. D. Van Nostran Co..

3. ^ Singmin, Andrew (2001). Beginning digital electronics through projects. Newnes. p. 9. ISBN 0750672696. "Signals come from transducers..."

4. ^ Miller, Mark R. (2002). Electronics the Easy Way. Barron's Educational Series. pp. 232–239. ISBN 0764119811. "Until the radio came along..."

5. ^ Hsu, Hwei Piao (2003). Schaum's outline of theory and problems of analogue and digital communications. McGraw-Hill Professional. p. 202. ISBN 0071402286. "The presence of noise degrades the performance of communication systems."

6. ^ Carr, Joseph J. (2000). Secrets of RF circuit design. McGraw-Hill Professional. p. 423. ISBN 0071370677. "It is common in microwave systems..."

7. ^ Roe, David B.; Wilpon, Jay G. (1994). Voice communication between humans and machines. U.S. National Academy of Science Press. p. 19. ISBN 0309049887. "...microelectronics technology."

8. ^ Chen, Wai-Kai (2005). The electrical engineering handbook. Academic Press. p. 101. ISBN 0121709600. "Noise from an analog (or small-signal) perspective..."

9. ^ Scherz, Paul (2006). Practical electronics for inventors. McGraw-Hill Professional. p. 730. ISBN 0071452816. "In order for analog devices... to communicate with digital circuits..."

10. ^ Williams, Jim (1991). Analog circuit design. Newnes. p. 238. ISBN 0750696401. "Even within companies producing both analog and digital products..."

Acoustics

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics can be seen in almost all aspects of modern society with the most obvious being the audio and noise control industries.

Hearing is one of the most crucial means of survival in the animal world, and speech is one of the most distinctive characteristics of human development and culture. So it is no surprise that the science of acoustics spreads across so many facets of our society—music, medicine, architecture, industrial production, warfare and more. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Lindsay's 'Wheel of Acoustics' is a well accepted overview of the various fields in acoustics.^[1]

The word "acoustic" is derived from the Greek word ἀκουστικός (akoustikos), meaning "of or for hearing, ready to hear"^[2] and that from ἀκουστός (akoustos), "heard, audible",^[3] which in turn derives from the verb ἀκούω (akouo), "I hear".^[4]

The Latin synonym is "sonic", after which the term sonics used to be a synonym for acoustics^[5] and later a branch of acoustics.^[6] Frequencies above and below the audible range are called "ultrasonic" and "infrasonic", respectively.

Divisions of acoustics

The table below shows seventeen major subfields of acoustics established in the PACS classification system. These have been grouped into three domains: physical acoustics, biological acoustics and acoustical engineering.

Physical acoustics	Biological acoustics	Acoustical engineering
Aeroacoustics General linear acoustics Nonlinear acoustics Structural acoustics and vibration Underwater sound	Bioacoustics Musical acoustics Physiological acoustics Psychoacoustics Speech communication (production; perception; processing and communication systems)	Acoustic measurements and instrumentation Acoustic signal processing Architectural acoustics Environmental acoustics Transduction Ultrasonics Room acoustics

See also

Academic Programs in Acoustics Acoustic (magazine) Acoustic emission Acoustic impedance Acoustic levitation Acoustic location Acoustic streaming Acoustic tags Acoustic thermometry Acoustic wave equation Audiology Auditory illusion Auditory system Diffraction Doppler effect Fisheries acoustics Helioseismology Lamb wave Linear elasticity The Little Red Book of Acoustics (in the UK) Medical ultrasonography

Music therapy Noise control Noise pollution Picosecond ultrasonics P-wave Phonon Pressure Wave Rayleigh wave S-wave Seismology Sonification Sonochemistry Sound pressure Soundproofing Shock wave Sonic boom Sonoluminescence Sound Structural acoustics Surface acoustic wave Thermoacoustics Wallace Clement Sabine Waves Wave equation

Accelerator physics

Accelerator physics deals with the problems of building and operating particle accelerators.

The experiments conducted with particle accelerators are not regarded as part of accelerator physics. These belong (according to the objectives of the experiments) to particle physics, nuclear physics, condensed matter physics, materials physics, etc. as well as to other sciences and technical fields. The types of experiments done at a particular accelerator and/or its other uses are largely constrained by the characteristics of the accelerator itself, such as energy (per particle), types of particles, beam intensity, beam quality, etc.

Accelerator physics itself is the study of the motion of the particle beam through the machine, control and manipulation of the beam, interaction with the machine itself, and measurements of the various parameters associated with particle beams.

See also

• Particle accelerator
• important publications in accelerator physics
• Beam emittance
• Radiation damping
• Strong focusing
• Superconducting Radio Frequency
• Paraxial approximation

External links

• UCB/LBL Beam Physics site
• BNL page on The Alternating Gradient Concept