• No results found

Design and implementation of a laboratory information system for cellular pharmacology

N/A
N/A
Protected

Academic year: 2022

Share "Design and implementation of a laboratory information system for cellular pharmacology"

Copied!
48
0
0

Loading.... (view fulltext now)

Full text

(1)

UPTEC X07 010

Examensarbete 20 p Februari 2007

Design and implementation of a laboratory information system for cellular pharmacology

Jonathan Alvarsson

(2)

Uppsala University School of Engineering

UPTEC X 07 010 Date of issue 2007-01

Author

Jonathan Alvarsson

Title (English)

Design and implementation of a laboratory information system for cellular pharmacology

Title (Swedish) Abstract

A laboratory information system for handling high-throughput drug screening and low- to medium-throughput bioassays in cancer research performed by small to medium-sized academic groups was designed and partly implemented. All parts except for the graphical user interface have been implemented. The system has functionality for keeping track of when who did what, and it provides an annotation system for the objects of the system. The system was implemented in Java using the object relational manager Hibernate and the lightweight framework Spring.

Keywords

Laboratory information system, cancer research, high-troughput screaning, Hibernate, Spring

Supervisors

Rolf Larsson

Uppsala University, Clinical Pharmacology Scientific reviewer

Mats Gustafsson

Uppsala University, Signals and Systems

Project name Sponsors

Language

English Security

ISSN 1401-2138 Classification

Supplementary bibliographical information

Pages

47

Biology Education Centre Biomedical Center Husargatan 3 Uppsala

Box 592 S-75124 Uppsala Tel +46 (0)18 4710000 Fax +46 (0)18 555217

(3)

Design and implementation of a laboratory information system for cellular pharmacology

Jonathan Alvarsson

jonathan.alvarsson@gmail.com

February 28, 2007

Svensk sammanfattning

Inom dagens cancerforskning ¨ ar en vanlig metod f¨ or att hitta intressanta l¨ akemedelskandidater att man s¨ oker igenom stora bibliotek av molekyler genom att testa dem emot cancerceller. Den h¨ ar genoms¨ okningen ¨ ar ofta automatiserad och genererar stora m¨ angder data. I detta examensarbete designades och p˚ ab¨ orjades implementeringen av ett informationssystem f¨ or att hantera den m¨ angd av data som genereras. Som bas anv¨ andes det ¨ oppna k¨ allkodsprojektet Bioclipse som inneh˚ aller funktioner f¨ or att hantera bioinformatisk data.

Systemet har funktionalitet f¨ or att se vilken anv¨ andare som har gjort vad och n¨ ar. Anv¨ andare kan ¨ aven skapa egna annoteringar till objekten i systemet.

F¨ or att underl¨ atta genomf¨ orandet testades varje komponent i systemet i en separat milj¨ o; p˚ a det viset kunde m˚ anga fel uppt¨ ackas tidigt i projektet.

En komplett upps¨ attning tester underl¨ attar ¨ aven vid f¨ or¨ andringar, d˚ a tappad funktionalitet direkt kan uppt¨ ackas med testerna.

Projektet kunde inte slutf¨ oras inom ramarna f¨ or detta examensar- bete. Vid examensarbetets slut var design och implementation av k¨ arnstrukturen f¨ or hela systemet utom de grafiska delarna, d¨ aribland in- matning av data och presentation av data och resultat, klart.

Examensarbete 20p, Civilingenj¨ orsprogrammet Bioinformatik

Uppsala Universitet

(4)

Contents

1 Introduction 2

1.1 Overview . . . . 2

1.1.1 Fluorometric microculture cytotoxicity assay . . . . 2

1.1.2 Screening using an annotated compound library . . . . 2

1.1.3 Dose response . . . . 2

1.1.4 Compound combination effects . . . . 2

1.1.5 Information systems . . . . 2

2 Specification and design 3 2.1 Graphical user interface . . . . 4

2.2 General structure of the system . . . . 4

2.3 Data structure specification . . . . 5

2.4 Data input . . . . 5

2.5 Managers . . . . 5

3 Software tools and techniques for solutions 7 3.1 General solutions . . . . 7

3.1.1 MySQL . . . . 7

3.1.2 Eclipse . . . . 7

3.1.3 Hibernate . . . . 8

3.1.4 Hibernate synchronizer . . . . 8

3.1.5 Spring . . . . 8

3.1.6 JUnit . . . . 9

3.1.7 Bioclipse . . . . 9

3.1.8 JEP . . . . 9

3.2 Special solutions . . . 10

3.2.1 Auditing . . . 10

3.2.2 Annotations . . . 10

3.2.3 Calculations . . . 10

3.3 Persistent objects . . . 11

3.4 Data Access Objects . . . 11

3.5 Managers . . . 11

3.6 Tests . . . 11

4 Summary 12

5 Future 12

6 Acknowledgements 12

A Appendix – Graphical user interface specification 14

(5)

February 28, 2007 1 Introduction

1 Introduction

The main aim of this project was to design and initiate the implementation of a laboratory infor- mation system (LIS) able to handle data from both the high-throughput drug screening and the low- to medium-throughput bioassays in cancer re- search performed by small to medium-sized aca- demic groups. A LIS is a data system that receives, processes, stores and delivers information generated by medical laboratories. This project has been car- ried out at the department of medical sciences at Uppsala University. The program was written in Java and use the functionality of the open source project Bioclipse as a base.

1.1 Overview

In current cancer research, large amounts of chemi- cal compounds are examined with regard to effects on cancer cells. This process consists of highly auto- mated high-throughput processes as well as focused biological evaluation of more limited extent. A few different approaches exist which constitute the core activities at the department. These are discussed in the following sections.

1.1.1 Fluorometric microculture cytotoxicity assay

The first instrument to be handled in the sys- tem is an automated machine, an Optimised Robot for Chemical Analysis (ORCA; Beckman Coulter) equipped with a multipurpose reader (FLUOstar Optima, BMG Labtech GmbH, Offenburg, Ger- many), for fluorometric microculture cytotoxicity assay (FMCA). FMCA estimates cell death by mea- suring the amount of non-fluorescent fluorescein di- acetate (FDA) having been transformed into a fluo- rescent by cells with intact cell membranes[1]. The measurements are performed on microtiter plates with 96 or 384 wells.

First, the wells on the plates are prepared with the drugs of interest; then they are seeded with cells and incubated. After incubation, the plates are centrifuged and washed and FDA is added, and af- ter further incubation, the fluoroscence is measured.

See figure 1 for a picture of the complete process.

1.1.2 Screening using an annotated com- pound library

Large amounts of compounds are collected in li- braries and tested on tumor cells. Highly potent drugs can be identified through screening, and hy- potheses about biological mechanisms can be gener-

ated from the pattern of activity in different model systems and by combining these data with gene- expression[2]. The current library consists of more than 6500 compounds. Screening data consist of flu- oroscence measurements for a few data points (often of one concentration) for each compound.

1.1.3 Dose response

Interesting compounds are subsequently tested at different concentrations, and survival of the cells are plotted as a function of the concentration in order to produce a dose response curve. From this curve, the EC

50

value can be calculated. EC

50

is defined as the statistically estimated concentration needed for 50% effect, in this case 50% cell death.

1.1.4 Compound combination effects It is also of interest to study the effects of combina- tions of identified active compounds. An additional compound may counteract drug resistance. That is, a cell resistant to drug A may be sensitive to a combination of drug A and drug B, since drug B neutralises the cell’s protection against drug A.

1.1.5 Information systems

At the moment, no satisfactory solution exists for dealing with all data generated in these processes.

A few separate systems are in use at the lab, neither of which fully meets everyday requirements.

SLIMS Small Laboratory Information System[3]

is an open source product very suitable for screen- ing data but it does not support operations such as constructing dose response curves. It contains some very nice tools such as the self-organising maps func- tionality, which is a way to generate a visual rep- resentation of the chemical space spanned by the compounds. It is thus possible to see if interesting compounds lie close together or far apart. Not much seems to be happening with it, since in the news section of the project’s webpage, the last update is from August 2004, although the latest version is from March 2006. SLIMS is implemented using the programming language Python.

Accord (Accelrys Software Inc.) is a complex sys-

tem that turned out to be quite difficult to adopt

to the daily work at the laboratory. It seems to be

able to do many tasks but is not user-friendly. It is

a powerful tool that does not really make up for the

(6)

Figure 1: Introduction to a few objects in the system and a brief description of the FMCA process.

In the system a plate type defines the size, number of columns and rows, of a plate. A plate layout defines where on the plate the controls and the compounds are to be placed. Based upon this plate layout a number of equal plates are made, conforming to a so-called “master plate” that defines which drugs are placed in which wells. Each one of these plates is seeded with one cell type and incubated. After incubation, the plate is centrifuged and washed, and fluorescein diacetate is added. Then the plate is washed again, and incubated once more, before fluoroscence generated from fluorescein diacetate transformed into a fluorescent by cells with intact cell membranes is measured with a microplate fluorometer.

learning and configuration cost with its functional- ity.

Some in-house Matlab code also exists for in- terpreting measurements on plates and for colour- coding the results. In conclusion, it has become apparent that a tailor-made laboratory information

system (LIS) is needed, and the Bioclipse project (see section 3.1.7) already contained a lot of the needed functionality, so it was deemed appropriate as a foundation. An advantage of the tailor-made solution is that the lab would keep the source code and be able to extend and perform changes to the implementation when needed in the future.

2 Specification and design

The first thing to do when starting a project like this is not to sit down with a computer and write code, but rather to sit down with a pen and paper, specify what the program should be able to do, and design a structure able to do it.

It is not really suitable to speak about a spe-

cial software development process approach — such

as the waterfall model[6] — for this project, since

the number of developers during this project has

been one. But an iterative process[7] supported by

tests and somewhat inspired by the programming

approach known as extreme programming[8] might

(7)

February 28, 2007 2 Specification and design

Figure 2: The overall structure of the program. See section 2.2 for a short description of all the components.

be a fair description of the approach.

This section deals with the definition of the graphical user interface, the functionality of the pro- gram, and data modelling.

2.1 Graphical user interface

As a start, a sketch-like specification of the graphi- cal user interface (GUI), containing components for working with data about the plates used in FMCA, was constructed (see appendix A). The develop- ment of the GUI specification was an iterative pro- cess were the program took form during interviews and discussions with future users. The specification is not to be regarded as an exact representation of how the system is going to look, but rather a spec- ification of the future functionality of the program illustrated by examples to help the reader get a feel- ing for how it may look. The GUI specification is not a finished document, but a document that has been used on a daily basis throughout the project, and thus contains parts that are likely to change.

2.2 General structure of the system

When building programs above a certain level of complexity, it is desirable to use standard compo- nents in order to be able to focus on the uniqueness of the problem at hand instead of already solved standard problems. It is a bad thing to become

stuck with one solution and not be able to switch to another, hence, the components of this kind of program tend to be ordered in layers, and in a per- fect world it would be possible to swap a component in a layer for another one. These layers also have the benefits of taking care of a smaller part of the problem, and being able to concentrate on that in a divide-and-conquer manner.

Figure 2 shows a graphical representation of the overall structure of the program. At one end is the graphical user interface (GUI) with buttons, text-fields and so on, and at the other end is the database.

There are mainly three differrent sorts of objects in the system, managers, persistent objects and data access objects. This follows the standards from the book Pro Spring[4] about implementing software using the Spring framework. Spring is a frame- work containing standard code helpful when build- ing Java programs above a certain level of complex- ity, for example programs that work with databases.

The GUI contains text fields, buttons and similar

components that call methods of manager-objects

in the business layer. These managers provide func-

tionality for operations such as creating a plate with

wells and all associated information objects. The

managers have names such as AnnotationManager,

SampleManager and PlateLayoutManager. They

work with many smaller persistent classes that con-

tain the actual data. The persistent classes repre-

(8)

Component Description

Plate type Defines the size (number of wells) of a plate

Plate layout Defines in which wells for example dilution series and controls are to be placed, also defines calculation functions

Master plate Defines which drugs are placed and by which concentrations (when working with dilution series) in which wells

Plate Defines which cell type has been seeded on the plate

Table 1: The different components stepwise constructed when creating a plate.

sent the data that are being stored in the database and have names such as Plate, Well and CellSam- ple. The actual storing and retrieving of data from the database is done by data access objects (DAOs).

The DAOs work on one or a few persistent object each, saving it and some related persistent objects, as specified in Hibernate’s mapping files. Hence, there are more persistent objects than there are DAOs. The DAOs have names such as PlateDAO, UserDAO, and ProjectDAO. The DAOs communi- cate with the object relational mapper (ORM), Hi- bernate in this case, when saving and loading the persistent objects from the database. Lastly, there is a relational database, saving and retrieving the data from disk.

In this project the Spring framework provides im- portant help in implementing the business layer and the data access objects. It contains standard code which eases the implementation of these layers.

2.3 Data structure specification

As the GUI was being sketched during discussions with the staff, in the background the process of constructing a data model able to handle all that functionality took place. Finding a structure for the data is also an iterative process. Hopefully, the model will tend to evolve towards something more and more obvious. But the path towards this

“obvious” goal is all but clear and many ideas are constantly set aside for better ones during the life- span of the program. The goal is that when new kinds of data need to be saved, adding them to the system should be possible without too much of a problem. The resulting class diagram for the per- sistent objects is shown in figure 3. If we study the classes Project and Experiment, handled by the ProjectManager, which can be found in the lower right corner of figure 3 we see among other things that both have a DAO. The red line with two dia- monds at each end means that a Project has Experi- ments and the Experiments correspond to a Project.

If we follow the black line coming out on top of them we see that both of the classes extends Ab- stractAuditableObject that extends AbstractAnno- tatableObject which extends AbstractBaseObject.

This means that Projects and Experiments are both annotatable and auditable. The dashed lines ap- pearing to the right of figure 3 symbolise the way the objects are created. For example a PlateLayout is created from a PlateType.

Plates with a number of different layouts are used, and a certain layout with a set of drugs are used many times but with different cells. To reduce the repetitive work when creating plates, a plate is cre- ated in a couple of steps, and each step is saved.

So when creating a new plate similar to one already created, the whole process will not have to be re- peated. The components corresponding to these dif- ferent steps are shown in table 1.

During the discussions, it became apparent that a system for specification of calculations to be per- formed at the plate and well level is needed. Two sorts of functions can be defined in the system, plate functions and well functions. Plate functions are functions acting on data from the whole (or a part of the) plate and well functions are calculated result values for a well. These are stored in the database as text strings containing mathematical formulas such as (a4 − a3)/a2. The variables are references to the raw data for the wells. More complicated functions that can be called from the calculation functions, such as a sum function that does not count wells marked as outliers, are planned.

2.4 Data input

Both compound data and result data are imported to the system from file. It should be possible both to type in drug data manually and to insert complete libraries with drug data from file into the system.

The actual results will always be imported from file.

2.5 Managers

During the design of the managers, the ideal which

was strived towards was a natural division into

groups of persistent objects where each persistent

object is managed by one manager. The blue boxes

in figure 3 correspond to the responsibility area of

each manager.

(9)

February 28, 2007 2 Specification and design

A b

s t

rac tB

ase O

bj

ec t

id

: l

ong

crea

t

or: U

ser

name:s

t

r i

ng

d

e l

ete d

: b

oo l

+ d

e l

e t

e ()

Ab

s t

rac tPl

a t

e

rows:

i

n t

we

ll

s: W

e ll

co

l

s

: i

nt

+ d

e l

e t

e () A

b

s t

rac t

S

amp l

e

samp

l

e C

on t

a i

ner: S

amp l

e C

on t

a i

ner M

easuremen t

res

u l

ts

: R

es

u l

t

i

ns t

rumen t

: I

ns t

rumen t

resu

ltT

ype

: R

esu ltT

ype

+ d

e l

e t

e ()

+ d

eep C

opy ()

R esu

lt

res

u l

t V

a l

u e

: fl

oat []

vers

i

on: i

n t

+ d

eep C

opy () R

esu ltT

ype

l

eng th

: i

n t

Ab

stract A

nnotata bl

e Obj

ect

a

b

s t

rac tA

nno t

a ti

on I

ns t

ances: Ab

s t

rac tA

nno t

a ti

on I

ns t

ance Ab

s t

rac tA

nno t

a ti

on I

ns t

ance

a

b

s t

rac tA

nno t

a t

a bl

e Obj

ec t

: A

b

s t

rac tA

nno t

a t

a bl

e Obj

ec t

mas

t

er A

nno t

a ti

on: A

nno t

a ti

on

F l

oa tA

nno t

a ti

on

va

l

ue: fl

oa t

+ d

eep C

opy () T

ex tA

nno t

a ti

on

va

l

ue:s t

r i

ng

+ d

eep C

opy ()

E num

A

nno t

a ti

on

va

l

ue: St

r i

ng

+ d

eep C

opy ()

A

u di

tL

og

user:

U

ser

t

i

me S

tamp

: d

o

u bl

e

au

ditT

ype: A

u ditT

ype

au

dit

e dObj

ec t

: Ab

s t

rac tA

u dit

a bl

e Obj

ec t

pos

tA

u ditR

epresen t

a ti

on:s t

r i

ng

+ d

e l

e t

e ()

I

ns t

rumen t

measuremen t

s: M

easuremen t

+ d

e l

e t

e ()

S

amp l

e C

on t

a i

ner

samp

l

es

: Ab

s t

rac tS

amp l

e

we

ll

: W

e ll

wor

kLi

s t

: W

or kLi

s t

+ d

eep C

opy ()

+ d

e l

e t

e ()

C

e llS

amp l

e

ce

llO

r i

g i

n

: C

e llO

r i

g i

n

d

e f

ros ti

ng D

a t

e: Ti

mes t

amp

+ d

eep C

opy () O

pera ti

on M

anager

A

u ditM

anager

P l

a t

e M

anager

S

amp l

e

M ar

k

er

a

b

s t

rac tS

amp l

e: Ab

s t

rac tS

amp l

e

we

ll

: W

e ll W

or k

L i

s t

a

b

s t

rac tO

pera ti

ons: Ab

s t

rac tO

pera ti

on

samp

l

e C

onta i

ner

: S

amp l

e C

onta i

ner

+ d

e l

e t

e ()

+ d

eep C

opy ()

Ab

s t

rac tO

pera ti

on

wor

kli

s t

: W

or kLi

s t

P l

a t

e L

ayou t

l

ay O

u tW

e ll

s: L

ayou tW

e ll

p

l

a t

e T

ype:

P l

a t

e T

ype

+ d

eep C

opy ()

+ d

e l

e t

e () Pl

a t

e T

ype

co

l

s

: i

nt

rows:

i

n t

p

l

a t

e L

ayou t

s

:

P l

a t

e L

ayou t

L

ayou t

W e

ll

l

ay O

u tM

ar k

ers: L

ay O

u tM

ar k

er

p

l

a t

e L

ayou t

:

P l

a t

e L

ayou t

+ d

eep C

opy ()

+ d

e l

e t

e () L

ay O

u t

M ar

k

er

l

ayou tW

e ll

: L

ayou tW

e ll

+ d

eep C

opy () P

l

a t

e L

ayou tM

anager

C

e llO

r i

g i

n

ce

llS

amp l

es: C

e llS

amp l

e

M as

t

er Pl

a t

e

l

oc k

e d

: b

oo l

+ d

eep C

opy ()

P

ro j

ec t

exper

i

men t

s: E

xper i

men t

+ d

e l

e t

e () P

ro j

ec tM

anager

« i

n t

er f

ace»

I Ab

s t

rac tB

ase Obj

ec t

W e

ll

F unc

ti

on

express

i

on:s t

r i

ng

we

ll

: Ab

s t

rac tW

e ll

+ d

eep C

opy ()

« enum»

A

u ditT

ype

C

REATE

_ EVENT

DELETE

_ EVENT

U

P DATE

_ EVENT

D rug

S

amp l

e

concen

t

ra ti

on

: d

ou bl

e

d

rug O

r i

g i

n: D

rug O

r i

g i

n

+ d

eep C

opy ()

O

r i

g i

n M

anager S

amp l

e M

anager

h

as

DAO

h

as

DAO h

as

DAO

h

as

DAO

h

as

DAO P

l

a t

e

F unc

t i

on

express

i

on: St

r i

ng

goo

dF

rom

: d

o

u bl

e

goo

dT

o: d

ou bl

e

h

as S

pec ifi

e dV

a l

ue

: b

oo l

p

l

a t

e: A

b

s t

rac tB

ase

P l

a t

e

+ d

eep C

opy ()

h

as

DAO

h

as

DAO

h

as

DAO

Pl

a t

e

b

arco d

e:s t

r i

ng

cura

t

e d

: b

oo l

exper

i

men t

: E

xper i

men t h

as

DAO

h

as

DAO

h

as

DAO

h

as

DAO

« enum»

A

nno t

a ti

on T

ype

TEXT

_

ANNOTATION

FLOAT

_

ANNOTATION

ENUM

_ ANN

O

TATI O

N A

nno t

a ti

on

poss

ibl

e V

a l

ues: S

e t

anno

t

a ti

on T

ype: A

nno t

a ti

on T

ype

+ d

e l

e t

e ()

h

as

DAO

h

as

DAO h

as

DAO

Ab

s t

rac t

W e

ll

we

llF

unc ti

ons: W

e llF

unc ti

on

co

l

: i

n t

row:c

h

ar

Ab

s t

rac tB

ase Pl

a t

e

p

l

a t

e F

unc t

i

ons:

P l

a t

e F

unc t

i

on Ab

s t

rac t

A

u di

t

a bl

e Obj

ec t

au

ditL

ogs: A

u ditL

og

U ser

passwor

d

:s t

r i

ng

au

diti

ngs: A

u ditL

og A

nno t

a ti

on M

anager

E xper

i

men t

pro

j

ec t

:

P ro

j

ec t

p

l

a t

es

:

P l

a t

e

+ d

e l

e t

e () W

e ll

samp

l

e C

on t

a i

ner

: S

amp l

e C

on t

a i

ner

samp

l

e M

ar k

ers: S

amp l

e M

ar k

er

ou

tli

er: b

oo l

p

l

a t

e: A

b

s t

rac t

P l

a t

e

+ d

eep C

opy ()

+ d

e l

ete ()

D rug

O

r i

g i

n

str

u ct

u re

: str

i

ng

d

rug S

amp l

es: D

rug S

amp l

e

mo

l

ecu l

ar W

e i

g ht

: d

ou bl

e

h

as

DAO

h

as

DAO

Figure 3: The class diagram of the persistent classes. The blue boxes represent the managers and show which classes are handled by which managers, abstract classes are green, interfaces are purple, enums

a

are red and instatiated classes are yellow. All the persistent classes implement the interface IAbstractBaseObject which is not shown in the diagram in order to clean it up a little and some (represented with black frames in the figure) also extend AbstractAuditableObject.

This diagram was created by the means of the software Umbrello[5].

aenums where introduced in Java 5. They are types with a predefined set of values. A prototypical example of an enum is dayOfWeek, which can take on the values Monday, Tuesday, . . . , Sunday.

(10)

Figure 4: The development environment Eclipse running JUnit tests.

3 Software tools and techniques for solutions

In order to complete this sort of program, a num- ber of software tools for system building are useful.

A database system is needed that can save and re- trieve data and support querying. Although code can be written in any editor, it is nice with a de- velopment platform which is able to really help the programmer. Here follows a list of software used or just evaluated during this project. This section con- tains more details about what tools and techniques where used for the implementation. A big part of this project has been to look for and learn different tools and techniques.

3.1 General solutions

3.1.1 MySQL

MySQL is an open source database management system (DBMS) developed by MySQL AB. MySQL is a relational DBMS, that is, it presents the data in relational form as tables, and it provides relational operators to manipulate the data[9, 10].

In this project, MySQL was chosen mainly be- cause it is well known, easy to install and well sup- ported. Not many other systems were ever seriously considered.

3.1.2 Eclipse

Eclipse is, in the words of its own webpage,

“an open source community whose projects are focused on providing a vendor-neutral open development plat- form and application frameworks for building software. The Eclipse Foun- dation is a not-for-profit corporation formed to advance the creation, evo- lution, promotion, and support of the Eclipse Platform and to cultivate both an open source community and an ecosystem of complementary products, capabilities, and services.”[11]

Eclipse is not only a development platform. Its com- munity also produces a plugin based platform, the Eclipse Rich Client Platform, that can be used to build any kind of program. Since Eclipse is open source and there are lots of people writing plugins for it a wide variety of plugin programs exists for it.

There are a few big development platforms for Java. Except for Eclipse, Borland’s JBuilder and Sun’s NetBeans are two that are commonly used.

Figure 4 shows Eclipse running JUnit tests.

References

Related documents

sign Där står Sjuhalla On a road sign at the side of the road one.. stands Sjuhalla 9.15.05 Then we

Even after clearing the flash from the outer surface of the weight plate by using a cutting tool, there will be a stick out of flash along the part line, by using different

registered. This poses a limitation on the size of the area to be surveyed. As a rule of thumb the study area should not be larger than 20 ha in forest or 100 ha in

Summing all the errors we may thus expect the standard error in the drop height estimate to be of an order around 1 % or less, and a major variation coming from the method of

The benefit of using cases was that they got to discuss during the process through components that were used, starting with a traditional lecture discussion

A plate tensegrity structure obtained with triangular elements will, as already noted, form a different overall geometry than with rectangular elements, if only

The collaboration between Anders Hagberg and Palestinian oud virtuoso Ahmad al Khatib has resulted in the album Melodic Melange (2014) where they play with Swedish bass

The measured temperature by PT approximately yields an effective temperature which can be used for predicting the heat transfer to surfaces exposed to radiation and