Kenneth Buckle, a visiting scientist at the Center
for Integrated Manufacturing Studies at the Rochester
Institute of Technology, provides this answer:
When connected to a load like a lightbulb, a typical battery
undergoes chemical reactions that release electrons, which
travel through the bulb and are then reabsorbed by the battery.
(Devices that store mechanical energy also exist, but the most
common bat ter ies ,  such as those used in fl  ashlights and   remotes,
hold energy in chemical form.) Inside is at least one galvanic
cell, which produces between zero and several volts,   depending
on its chemistry. In a car battery, six cells, each contributing
two volts, are connected in series to make a 12-volt battery.
All electrochemical cells consist of two electrodes separated
by some distance. The space between the electrodes is fi  lled
with an electrolyte, a liquid or
solid containing charged par-
ticles, or ions. One electrode—
the anode—emits negatively
charged electrons. The other—
the cathode—receives them.
Chemical differences between
the two electrodes create an en-
ergy difference, or potential,
that moves electrons from the
anode to the cathode via the
electrolyte. For example, the lead-acid cell uses a lead oxide
cathode, a lead anode and a sulfuric acid (liquid) electrolyte.
In this case, sulfuric acid creates an environment that
stretches the chemical bonds of the lead and lead oxide, so
oxidation and reduction reactions occur simultaneously. In the
reduction reaction the acid strips the oxygen from the lead-
oxide cathode and replaces it with sulfate. The oxide ion then
combines with hydrogen (from the acid) and forms water. In
oxidation the sulfuric acid coaxes two electrons away from the
lead and then latches on to form lead sulfate. If the battery is
attached to a load, the electrons that the sulfate replaces   travel
out of the cell and into the load, creating an electric current.
A galvanic cell can continue to discharge electrons until
either or both electrodes run out of reagents, the compounds
that drive the oxidation/reduction reactions. In a nonrecharge-
able battery the chemical reaction that created the energy is
not easily reversible, and when the reagents run out the cell is
unusable. In a rechargeable battery, such as the lead-acid cell,
the reaction is reversible, meaning that an external source of
direct electric current can force the electrons to fl  ow from the
cathode to the anode until the cell is recharged.
Does damp weather make
arthritis pain worse?
—C. Levy, Falls Church, Va.
Donald A. Redelmeier, a professor of medicine at
the University of Toronto, explains:
Despite the commonly held notion that dampness contrib-
utes to joint aches, decades of medical research show no ob-
jective relation between arthritis severity and weather.
Dampness, decreases in barometric pressure and high hu-
midity are characteristics that some people believe contribute
to fl  ares in arthritis pain, but similar environmental changes
experienced during other situations do not seem to affect suf-
ferers one way or the other. For instance, arthritis patients do
not experience dramatic increases in symptoms when bathing
or swimming. Patients easily tolerate greater swings in pres-
sure during a plane ride than would occur during a storm.
Still, no past study investigating the link between weather
and arthritic pain is fl  awless; research has neither totally ruled
out nor established a connection. Evidence of a causal link
requires dispassionate observation wherein neither clinicians
nor patients know what exposure is active. Clinicians and pa-
tients would have to ignore weather—a diffi  cult task.
Studies suggest people see patterns even where none exist.
By chance, some rainy days will be followed by pain, en-
trenching the belief in a connection. Ultimately, such beliefs
reveal more about the workings of the mind than those of
the body

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ABSTRACT
The results of bottle and mesocosm experiments
were compared with those obtained in whole-
ecosystem experiments at the Experimental Lakes
Area. Unless they can be cleverly designed to mimic
major ecosystem processes and community compo-
sitions, smaller-scale experiments often give highly
replicable, but spurious, answers. Problems with
appropriate scaling are difficult to deduce without
direct comparisons with whole-ecosystem experi-
ments. Reasons aremany, but include inappropriate
spatial scales to include whole communities, in
particular predators and nocturnally active animals;
temporal scales that are too short to assess accu-
rately the response of slow-responding organisms
and biogeochemical processes; and elimination of
key littoral–pelagic and catchment–lake interac-
tions. Identical studies of limnological processes in
lakes of a large range of sizes reveals that scaling
correction is also necessary when extrapolating
from small lakes to large ones. Accurate manage-
ment decisions cannot be made with confidence
unless ecosystem scales are studied.
Key words: mesocosms; ecosystem experiments;
Experimental Lakes Area; spatial and temporal
scales.

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Economists are widely viewed by the general public
as being committed tomarkets as a way of allocating
resources and consequently to the use of market
prices as a reflection of social value. This view has
given economists a bad reputation in some circles;
indeed, there is a cynical definition of an economist
as someone who ‘‘knows the price of everything and
the value of nothing.’’ Whereas economists prob-
ably do as a group have more faith in markets than
others, it certainly is not true that we equate price
with value. We recognize many goods and services
for which there are no markets (such as clean air,
wildlife habitat, and fishing stocks) as having value.
Furthermore, for some market-traded goods, we
recognize that price is not a good measure of value
due to the presence of externalities; for example,
with electricity produced from the burning of coal
that generates air pollution the price of electricity
does not reflect the social cost imposed through
pollution.
However, even when market price is inadequate,
we find it useful to work with a ‘‘price-like’’ concept
in dealing with allocation problems. This is partly
because good decision making requires a means of
measuring the value of market and nonmarket
goods in commensurate units. For example, in
deciding whether or not to allow an additional
coal-fired plant, we need to measure the cost of
pollution in units comparable to themarket value of
energy.We refer to the cost per unit of pollution as a
‘‘shadow price.’’
The determination of shadow prices is an inexact
science on which there is an extensive literature.
Because many of the ways of determining these
values are discussed elsewhere in this volume, I will
confine my remarks to a few generalities and one
important example. In a democratic society, values
used in public decision making should reflect values
held by individual citizens. Formanymarket-traded
goods, we can argue that market prices are the right
measures because individuals trade off at the mar-
gin amounts of apples and oranges, for example, to
purchase based on their relative expense (price).
However, for goods not traded on markets (such as
clean air), other methods must be devised for
determining consumer willingness to pay for them
in terms of market goods. The resulting weights are
referred to as shadow prices because they play the
same role in allocation as do market prices for
traded goods.
When there are no markets on which people can
directly exercise their preferences, shadow pricing is
more difficult, and there are pitfalls. We can try, to
ask people how they would value a hypothetical
change in biological diversity, for example, but if
such people are not well informed about possible
consequences, theymay not give good answers, and
even if well informed, research has found that
people are not very good at thinking about hypo-
thetical situations—in particular, the answers they
give vary widely as a function of how the questions
are asked. Economists are more comfortable if
preferences can be inferred from decisions actually
taken (as is the case formarket goods). For example,
we can infer something about the value placed on
clean air by looking at the differences in land rents
on clean versus dirty sites. Unfortunately, however,
these methods too are rather imprecise. Our posi-
tion is, however, that having some estimates is
better than having none, and even ballpark esti-
mates can help inmaking informed decisions. Econo-
mists are constantly working to improve the neces-
sary methodology

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ABSTRACT
The nitrogen (N) cycle of forest ecosystems is un-
derstood relatively well, and few scientists expect
that major revisions will be necessary; most current
work on N cycling focuses on improving the preci-
sion estimates of pools and fluxes, or measuring the
magnitudes of well-known pools in response to
management or disturbances. However, in the past
few decades more than a dozen articles in refereed
journals have claimed very high rates of N input, far
beyond the rates expected for known sources of N.
In this review, we summarize the literature on N
accretion rates in forests that lack substantial con-
tributions from symbiotic N-fixing plants. We cri-
tique each study for the strength of the experimen-
tal design behind the estimate of N accretion and
consider whether unexpectedly large inputs of N
really occur in forests. Only 6 of 24 estimates of N
accretion had strong experimental designs, and
only 2 of these 6 yielded estimates of .5kg
Nha-1
y-1
. The high accretion estimates with a
strong experimental design come from repeated
sampling at the Walker Branch watersheds in Ten-
nessee, where N accretion rates ranged from 50 to
80 kg N ha-1
y-1
over 15 years after harvesting. At
the same location, an unharvested stand showed no
significant change. We conclude that there is no
widespread evidence of high rates of occult N input
in forests. Too few studies have carefully tested for
balanced N budgets in forests (inputs minus outputs
plus change in storage), and we recommend that at
least a few of these studies be undertaken on soils
that permit high precision sampling.

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and Eugene P. Odum

Valuation is one mechanism by which humans
organize occupancy and use of large-scale ecosys-
tems and regions, such as watersheds, estuaries,
cities, states, nations, and ultimately the whole
earth (the global perspective). When human valua-
tions do not measure the real contributions of
natural ecosystems, as is currently the case, ecosys-
tems are not protected, and the larger systems
produce less when the natural ecosystems are lost to
development. Ecologists working on small-scale
studies are concerned with the loss of their study
areas and biodiversity. Ecologists working at large
scales, and society in general, have to be concerned
that poor valuation is delaying the organization of a
sustainable pattern of environment and people.
Ecosystems of the world are threatened because
market prices are used to evaluate them. As Figure 1
shows, money is only paid to people for their
contributions, and not to ecosystems. In fact, mar-
ket values are inverse to contributions. When soils,
wood, and other environmental products are abun-
dant, they contribute the most, but market value is
small.When environmental products are scarce, the
market value is high. Economic valuation, as cur-
rently practiced, can never be used appropriately to
evaluate environmental capital, its contributions, or
its impacts.
Efforts by economists and others have been made
in the last two decades to ‘‘internalize the externali-
ties’’ or to modify market valuation to give more
consideration to ecosystems. What is needed is the
reverse: to ‘‘externalize the internalities’’ to put the
contributions of the economy on the same basis as
the work of the environment. We suggest that thebestway to do this is to use one kind of energy as the
common denominator.
As reviewed by Martinez-Alier (1987), beginning
in the middle of the last century investigators have
attempted to evaluate environmental products with
energy. These attempts failed because different kinds
of energies were considered equal. A calorie of
sunlight, wind, coal, hydrogen, plants, animals, and
people was considered equal, though they definitely
are not equal. The early evaluations ignored the
natural energy hierarchy of the universe in which
many joules of one kind must be degraded to
generate a few joules of another. Ecologists are
familiar with the food chain example of energy
hierarchy and know that a joule of a whale involves
more prior work than a joule of phytoplankton.
Also, until recently, mainline economists ignored
any suggestions for including nature’s goods and
services in economic valuation, even suggestions
from members of their own profession, such as
Kenneth Boulding’s (1962) plea for a ‘‘reconstruc-
tion of economics’’ in the 1960s. The time had not
yet come for reforms.
Starting in 1967, a method of valuation was
developed based on the total amount of energy of
one kind used directly and indirectly (and by all
pathways) necessary to make something. For ex-
ample, everything in an ecosystemcan be expressed
in the solar energy used to make each item by
various direct and indirect pathways. Thus, fish
have higher values per joule than phytoplankton.
The first of these valuations were of agroecosys-
tems and marshes (HT Odum 1967, 1971; EP Odum
and HT Odum 1972; Gosselink and others 1974). In
1975, the concept now called ‘‘transformity,’’ which
measures the quality of energy and its location in

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INTRODUCTION
As long as we are forced to make choices, we are
doing valuation. But different approaches to valua-
tion are based on qualitatively different assump-
tions. For example, the economics approach to
valuation is based on the ethical principle of con-
sumer sovereignty, and it privileges the kinds of
decisions individuals make in the marketplace. We
accept the economics approach as a useful partial
approach to decision making in relation to ecosys-
temservices if one is interested in what people think
about and want from services; if one believes that
human preferences are the basis for the value of
services; if one accepts the assumption that adding
individual preferences reflects humanity’s collective
valuation of ecosystemservices and life support; and
if one assumes that marginal changes will only
cause marginal consequences.
The thesis of this article is that currently used
modes of valuing ecosystem services do not take
into account the inherent complexities and result-
ing uncertainties associated with dynamics of these
coupled systems of people and nature. Ecosystem
services are not a smooth, controllable function of
human controls; rather, the nonlinearities and shift-
ing relationships of these systems create changes
that are inherently unpredictable. Human values
and preferences are not static and pre-existent;
rather, they are formed in interaction with nature
and with society. Those types of uncertainties are
difficult to capture with current modes of valuation.
We end with some modest suggestions of institu-
tional solutions to deal with those uncertainties.We

begin with a weak typology of various goals of
ecosystem valuation.

WHAT IS VALUATION ‘‘FOR’’?
Economic valuation of natural systems and their
services is undertaken for at least three reasons.
First, a study may attempt to show that natural
systems are indisputably linked to human welfare,
even when they are priced at zero. This is the sense
in which we understand recent efforts to value the
whole earth (for example, Costanza and others
1997)—the lesson learned is that the significance of
natural systems for economic well-being is real and
large and that it therefore must be taken into
account. The focus is not on a single number that
describes the worth of an ecosystem but on the
myriad ways in which human systems and natural
systems influence and undergird one another. The
goal is to make sure that ‘‘nature’’ is represented in
decision-making processes and to note that its role
in the economy is not merely aesthetic.
Second, economic valuation may be undertaken
to describe the relative importance of various ecosys-
tem types. For example, the special significance of
wetlands for the economy has been amajor result of
ecological and economic valuation studies (for ex-
ample, Odum 1984; Farber and Costanza 1987;
Turner and others 1995). The lesson that wetlands
are especially valuable has been embedded in legal
and institutional systems, leading to their relative
protection from development and agricultural im-
pacts and direct modifications. In this case, eco-
nomic valuation results were adduced as evidence
supporting an already well-established ecological
intuition about the importance of wetland function
for society.

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Generating laterally ordered, ultradense, macroscopic arrays of nanoscopic elements will
revolutionize the microelectronic and storage industries. We used faceted surfaces of commercially
available sapphire wafers to guide the self-assembly of block copolymer microdomains into
oriented arrays with quasi–long-range crystalline order over arbitrarily large wafer surfaces.
Ordered arrays of cylindrical microdomains 3 nanometers in diameter, with areal densities in
excess of 10 terabits per square inch, were produced. The sawtoothed substrate topography
provides directional guidance to the self-assembly of the block copolymer, which is tolerant of
surface defects, such as dislocations. The lateral ordering and lattice orientation of the single-grain
arrays of microdomains are maintained over the entire surface. The approach described is parallel,
applicable to different substrates and block copolymers, and opens a versatile route toward
ultrahigh-density systems.

Producing a surface with an ultradense ar-
ray of addressable nanoscopic elements that
is perfectly ordered over macroscopic length
scales is a formidable challenge. The self-assembly
of block copolymers (BCPs), two chemically dis-
similar polymers joined together, is emerging
as a promising route to generate templates and
scaffolds for the fabrication of nanostructured
materials and offers a potential solution to this
challenge (1–3). Despite the substantial advances
that have been made to enhance the lateral or-
dering of the BCP microdomains in thin films,
achieving perfect order over macroscopic length
scales has not been possible (4–7). In thin films,
BCPs self-assemble into grains, tens of microns
in size, of laterally ordered nanoscopic micro-
domains. Electron beam (e-beam) lithography
is a serial writing process, and although slow,
has been successfully used to produce nano-
scopic chemical or topographic surface patterns
that can be used to guide the self-assembly of

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1. Introduction
Compositionally step-graded metamorphic layers, changing
the composition of epilayers along the direction of epilayer
growth step-by-step, have received considerable attention as
buffer layers for large lattice mismatch epilayers on GaAs
substrate [1]. This buffer can accommodate the large lattice
mismatch between the active layer and the GaAs substrate
by the formation of misfit dislocations, isolate these misfit
dislocations and prevent their propagation into the active layer
grown on the buffer [2–4]. It is widely used as buffer layer for
microelectronic devices, such as metamorphic high electron
mobility transistor (MM-HEMT) [5] and heterojunction
bipolar transistors (HBT) [6]. Various metamorphic buffer
3 Author to who any correspondence should be addressed.
layers have been grown onGaAs substrate, such as InGaAs [7],
InAlAs [8], InGaP [9], AlGaInAs [10] or AlGaAsSb [5].
Among these materials, InAlAs metamorphic buffer layers
have many advantages, for example, Al containing buffer has
less leakage current than that of InGaAs, i.e. the presence of
Al improves the insulating properties [3]. However, owing
to the presence of Al content, the crystalline and optical
properties of the InAlAs layer is found to be rather poor.
Furthermore, clustering effect seems to occur, due to the large
difference between the In–As and Al–As bond energies [11].
The amount of clustering is expected to be strongly dependent
on growth conditions (growth temperature, V/III ratio,etc)
particularly the growth temperature. The metamorphic step-
graded buffer layers were usually grown at low temperature
(LT) (Ts
400 ◦
C) to avoid island formation, confine themajority of dislocations
to within the buffer layers, prevent
their propagation into upper layers [12, 13], significantly
suppress buffer leakage current and miscibility gap clustering
in InAlAs [14]. LT growth method can change the strain
relaxation dramatically and incorporate a very high density
of defects [15], furthermore, device applications often require
high resistivity, low lifetime material to act as buffers for
electrical isolation and reducation of backgating and sidegating
[16]. The step-graded buffer layer filter dislocations more
easily as growth proceeds than the linearly graded InAlAs
buffer layer [17]. In xAl1−x As epilayers with the In
composition of x=0.52 are mainly used as barrier layers due
to their large band gap (1.45 eV at 300K). In0.52Al0.48 As
(hereafter written as InAlAs) whose lattice matches the InP
substrate and In0.53Ga0.47 As(hereafter written as InGaAs)
active layer for long wavelength communication systems [18].
Some groups researched the InAlAs epilayer grown on InP
at a low temperature [11, 18], but few reports were focused
on low temperature step-graded InAlAs/GaAs metamorphic
buffer grown by molecular beam epitaxy(MBE).
In this paper, we study the characterization of step-graded
InAlAs buffer on the GaAs substrate under a selected range
of growth parameters. The influence of growth parameters is
studied by high-resolution x-ray diffraction(HRXRD), atomic
force microscopy(AFM) and photoluminescence(PL).The
electrical properties of the InAlAs/ InGaAs/GaAsMM-HEMT
structure grown on low-temperature step-graded InAlAs
metamorphic buffer layers are reported.

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Electronic confinement at nanoscale dimensions remains a central means of science and
technology. We demonstrate nanoscale lateral confinement of a quasi–two-dimensional electron
gas at a lanthanum aluminate–strontium titanate interface. Control of this confinement using an
atomic force microscope lithography technique enabled us to create tunnel junctions and field-effect
transistors with characteristic dimensions as small as 2 nanometers. These electronic devices can be
modified or erased without the need for complex lithographic procedures. Our on-demand
nanoelectronics fabrication platform has the potential for widespread technological application.

Controlling electronic confinement in the
solid state is increasingly challenging as
the dimensionality and size scale are
reduced. Bottom-up approaches to nanoelectron-
ics use self-assembly and templated synthesis;
examples include junctions between self-assembled
molecule layers (1, 2), metallic and semicon-
ducting quantum dots, carbon nanotubes (3–6),
nanowires, and nanocrystals (7, 8). Top-down
approaches retain the lithographic design motif
used extensively at micrometer and submicro-
meter scales and make use of tools such as
electron-beam lithography, atomic force micros-
copy (AFM) (9), nanoimprint lithography (10),
dip-pen nanolithography (11), and scanning
tunneling microscopy (12). Among the top-down
approaches, those that begin from modulation-
doped semiconductor heterostructures have led
to profound scientific discoveries (13, 14).
The interface between polar and nonpolar
semiconducting oxides displays remarkable
properties reminiscent of modulation-doped semi-
conductors (15–21). When the thickness of the
polar insulator (e.g., LaAlO3) exceeds a critical
value (dc = 3 unit cell), because of the polarization
discontinuity at the interface, the potential
difference across LaAlO3 will generate a “polar-
ization catastrophe” and induce the formation of a
quasi–two-dimensional electron gas (q-2DEG) at
the interface joining the two insulators (17). In
addition to the key role played by the polar dis-
continuity, there is evidence that, when present,
oxygen vacancies in the SrTiO3 also contribute to
the formation of the electron gas (22, 23).
We focus on LaAlO3-SrTiO3 heterostructures.
Because of the large conduction-band offset
between LaAlO3 and SrTiO3, the q-2DEG is
confined largely within the first few unit cells of
SrTiO3 (22, 24), with very little penetration into
the LaAlO3 layer (25). Electric fields have been
used to control the metal-insulator transition at
room temperature (17) and the superconductor-
insulator transition at cryogenic temperatures (21).
Further in-plane confinement of the q-2DEG has
been achieved by lithographically modulating the
thickness of the crystalline LaAlO3 layer (26).
Control over the metal-insulator transition at
scales of <4 nm was demonstrated by means of
a conducting AFMprobe (24). This latter method
forms the basis for the results reported below.

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