diff --git a/src/config.hpp b/src/config.hpp
index 28f8bcd..b046e2f 100644
--- a/src/config.hpp
+++ b/src/config.hpp
@@ -1,6 +1,7 @@
 #ifndef __COSMOTOOL_CONFIG_HPP
 #define __COSMOTOOL_CONFIG_HPP
 
+#include <string>
 #include <stdint.h>
 #include <exception>
 #include <cstring>
@@ -50,14 +51,19 @@ namespace CosmoTool
   class Exception : public std::exception
   {
   public:
-    Exception(const char *mess = 0)
-      : msg(mess) {}
+    Exception(const std::string& mess)
+      : msg(mess), msgok(true) {}
+    Exception()
+      : msgok(false) {}
 
-    const char *getMessage() const { return msg != 0 ? msg : "No message"; };
-    virtual const char *what() const throw () { return msg != 0 ? msg : "What 'what' ?"; };
+    virtual ~Exception() throw () {}
+
+    const char *getMessage() const { return msgok ? msg.c_str() : "No message"; };
+    virtual const char *what() const throw () { return msgok ? msg.c_str() : "What 'what' ?"; };
 
   private:
-    const char *msg;
+    std::string msg;
+    bool msgok;
   };
 
   /**
@@ -67,8 +73,10 @@ namespace CosmoTool
   class InvalidArgumentException : public Exception
   {
   public:
-    InvalidArgumentException(const char *mess = 0)
+    InvalidArgumentException(const std::string& mess)
       : Exception(mess) {}
+    InvalidArgumentException()
+      : Exception() {}
   };
 
   /**
@@ -76,8 +84,10 @@ namespace CosmoTool
   class InvalidRangeException : public Exception
   {
   public:
-    InvalidRangeException(const char *mess = 0)
+    InvalidRangeException(const std::string& mess)
       : Exception(mess) {}
+    InvalidRangeException()
+      : Exception() {}
   };
   
   /**
@@ -85,8 +95,10 @@ namespace CosmoTool
   class NoSuchFileException : public Exception
   {
   public:
-    NoSuchFileException(const char *mess = 0)
+    NoSuchFileException(const std::string& mess)
       : Exception(mess) {}
+    NoSuchFileException()
+      : Exception() {}
   };
 
   /**
@@ -94,22 +106,28 @@ namespace CosmoTool
   class InvalidFileFormatException : public Exception
   {
   public:
-    InvalidFileFormatException(const char *mess = 0)
+    InvalidFileFormatException(const std::string& mess)
       : Exception(mess) {}
+    InvalidFileFormatException()
+      : Exception() {}
   };
 
   class EndOfFileException: public Exception
   {
   public:
-    EndOfFileException(const char *mess = 0)
+    EndOfFileException(const std::string& mess)
       : Exception(mess) {}
+    EndOfFileException()
+      : Exception() {}
   };
 
   class FilesystemFullException: public Exception
   {
   public:
-    FilesystemFullException(const char *mess = 0)
+    FilesystemFullException(const std::string& mess)
       : Exception(mess) {}
+    FilesystemFullException()
+      : Exception() {}
   };
 };
 
diff --git a/src/powerSpectrum.cpp b/src/powerSpectrum.cpp
index 6ad7c89..9f3d7c8 100644
--- a/src/powerSpectrum.cpp
+++ b/src/powerSpectrum.cpp
@@ -21,7 +21,7 @@ using namespace std;
 #define POWER_BDM 7
 #define POWER_TEST 8
 
-#define POWER_SPECTRUM POWER_EFSTATHIOU
+#define POWER_SPECTRUM HU_WIGGLES
 
 namespace Cosmology {
 
diff --git a/src/yorick.cpp b/src/yorick.cpp
index 65ed7c5..ac8556a 100644
--- a/src/yorick.cpp
+++ b/src/yorick.cpp
@@ -142,10 +142,10 @@ public:
 namespace CosmoTool {
   template<typename T>
   ProgressiveOutput<T>
-  ProgressiveOutput<T>::saveArrayProgressive(const char *fname, uint32_t *dimList,
+  ProgressiveOutput<T>::saveArrayProgressive(const std::string& fname, uint32_t *dimList,
 					     uint32_t rank)
   {
-    NcFile *f = new NcFile(fname, NcFile::Replace);
+    NcFile *f = new NcFile(fname.c_str(), NcFile::Replace);
     
     assert(f->is_valid());
     
@@ -171,10 +171,10 @@ namespace CosmoTool {
 
   template<typename T>
   ProgressiveInput<T>
-  ProgressiveInput<T>::loadArrayProgressive(const char *fname, uint32_t *&dimList,
+  ProgressiveInput<T>::loadArrayProgressive(const std::string& fname, uint32_t *&dimList,
 					      uint32_t& rank)
   {
-    NcFile *f = new NcFile(fname, NcFile::ReadOnly);
+    NcFile *f = new NcFile(fname.c_str(), NcFile::ReadOnly);
 
     assert(f->is_valid());
 
@@ -193,10 +193,10 @@ namespace CosmoTool {
   }
 
   template<typename T>
-  void saveArray(const char *fname,
+  void saveArray(const std::string& fname,
 		 T *array, uint32_t *dimList, uint32_t rank)
   {
-    NcFile f(fname, NcFile::Replace);
+    NcFile f(fname.c_str(), NcFile::Replace);
     
     assert(f.is_valid());
     
@@ -217,11 +217,11 @@ namespace CosmoTool {
   }
 
   template<typename T>
-  void loadArray(const char *fname,
+  void loadArray(const std::string& fname,
 		 T*&array, uint32_t *&dimList, uint32_t& rank)
 	throw (NoSuchFileException)
   {
-    NcFile f(fname, NcFile::ReadOnly);
+    NcFile f(fname.c_str(), NcFile::ReadOnly);
     
     if (!f.is_valid())
       throw NoSuchFileException(fname);
@@ -251,18 +251,18 @@ namespace CosmoTool {
   template class ProgressiveOutput<float>;
   template class ProgressiveOutput<double>;
 
-  template void loadArray<int>(const char *fname,
+  template void loadArray<int>(const std::string& fname,
 			       int*& array, uint32_t *&dimList, uint32_t& rank);
-  template void loadArray<float>(const char *fname,
+  template void loadArray<float>(const std::string& fname,
 				 float*& array, uint32_t *&dimList, uint32_t& rank);
-  template void loadArray<double>(const char *fname,
+  template void loadArray<double>(const std::string& fname,
 				  double*& array, uint32_t *&dimList, uint32_t& rank);
 
-  template void saveArray<int>(const char *fname,
+  template void saveArray<int>(const std::string& fname,
 			       int *array, uint32_t *dimList, uint32_t rank);
-  template void saveArray<float>(const char *fname,
+  template void saveArray<float>(const std::string& fname,
 				 float *array, uint32_t *dimList, uint32_t rank);
-  template void saveArray<double>(const char *fname,
+  template void saveArray<double>(const std::string& fname,
 				  double *array, uint32_t *dimList, uint32_t rank);
   
 }
diff --git a/src/yorick.hpp b/src/yorick.hpp
index f124ae8..25734f7 100644
--- a/src/yorick.hpp
+++ b/src/yorick.hpp
@@ -4,6 +4,7 @@
 #include "config.hpp"
 #include <stdint.h>
 #include <fstream>
+#include <string>
 
 
 namespace CosmoTool 
@@ -77,8 +78,8 @@ namespace CosmoTool
 
   public:
     static ProgressiveInput<T> 
-      loadArrayProgressive(const char *fname, uint32_t *&dimList, 
-			   uint32_t& rank);
+    loadArrayProgressive(const std::string& fname, uint32_t *&dimList, 
+			 uint32_t& rank);
 
     ProgressiveInput() {
       impl = 0; 
@@ -143,8 +144,8 @@ namespace CosmoTool
 
   public:
     static ProgressiveOutput<T> 
-      saveArrayProgressive(const char *fname, uint32_t *dimList, 
-			   uint32_t rank);
+    saveArrayProgressive(const std::string& fname, uint32_t *dimList, 
+			 uint32_t rank);
 
     ProgressiveOutput() {
       impl = 0; 
@@ -181,11 +182,11 @@ namespace CosmoTool
   };
 
   template<typename T>
-  void saveArray(const char *fname,
+  void saveArray(const std::string& fname,
 		 T *array, uint32_t *dimList, uint32_t rank);
 
   template<typename T>
-  void loadArray(const char *fname,
+  void loadArray(const std::string& fname,
 		 T*& array, uint32_t *& dimList, uint32_t& rank)
     throw (NoSuchFileException);