diff --git a/htroot/imagetest.java b/htroot/imagetest.java
index 73a7e9874..e2371c0c9 100644
--- a/htroot/imagetest.java
+++ b/htroot/imagetest.java
@@ -75,7 +75,7 @@ public class imagetest {
         img.setColor(RasterPlotter.BLUE);
         img.dot(620, 200, 90, true, 100);
         img.setColor(RasterPlotter.RED);
-        img.arc(300, 270, 30, 70, 0, 360);
+        img.arc(300, 270, 30, 70, 100);
         img.setColor("330000");
         img.arc(220, 110, 50, 90, 30, 110);
         img.arc(210, 120, 50, 90, 30, 110);
@@ -99,7 +99,7 @@ public class imagetest {
             }
         }*/
         img.setColor("0000A0");
-        img.arc(550, 400, 40, 81, 0, 360);
+        img.arc(550, 400, 40, 81, 100);
         img.setColor("010100");
         for (int i = 0; i <= 360; i++) {
             img.arc(550, 400, 40, 41 + i/9, 0, i);
diff --git a/source/de/anomic/yacy/graphics/NetworkGraph.java b/source/de/anomic/yacy/graphics/NetworkGraph.java
index eb064b818..fa1d9c586 100644
--- a/source/de/anomic/yacy/graphics/NetworkGraph.java
+++ b/source/de/anomic/yacy/graphics/NetworkGraph.java
@@ -186,7 +186,7 @@ public class NetworkGraph {
 
         // draw network circle
         networkPicture.setColor(COL_DHTCIRCLE);
-        networkPicture.arc(width / 2, height / 2, innerradius - 20, innerradius + 20, 0, 360);
+        networkPicture.arc(width / 2, height / 2, innerradius - 20, innerradius + 20, 100);
 
         //System.out.println("Seed Maximum distance is       " + yacySeed.maxDHTDistance);
         //System.out.println("Seed Minimum distance is       " + yacySeed.minDHTNumber);
@@ -343,7 +343,7 @@ public class NetworkGraph {
                     img.arcArc(centerX, centerY, innerradius, angle, dotsize + radius, dotsize + radius, a, a + 180/segments);
                 }
             } else {
-                img.arcArc(centerX, centerY, innerradius, angle, dotsize + radius, dotsize + radius, 0, 360);
+                img.arcArc(centerX, centerY, innerradius, angle, dotsize + radius, dotsize + radius, 100);
             }
         }
     }
diff --git a/source/de/anomic/yacy/graphics/OSMTile.java b/source/de/anomic/yacy/graphics/OSMTile.java
index e46f41ab7..8d3c0e78b 100644
--- a/source/de/anomic/yacy/graphics/OSMTile.java
+++ b/source/de/anomic/yacy/graphics/OSMTile.java
@@ -137,7 +137,7 @@ public class OSMTile {
             // see http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
             this.zoom = zoom;
             this.xtile = (int) Math.floor((lon + 180) / 360 * (1 << zoom));
-            this.ytile = (int) Math.floor((1 - Math.log(Math.tan(lat * Math.PI / 180) + 1 / Math.cos(lat * Math.PI / 180)) / Math.PI) / 2 * (1 << zoom));
+            this.ytile = (int) Math.floor((1 - Math.log(Math.tan(lat * RasterPlotter.PI180) + 1 / Math.cos(lat * RasterPlotter.PI180)) / Math.PI) / 2 * (1 << zoom));
         }
         
         public tileCoordinates(final int xtile, final int ytile, final int zoom) {
diff --git a/source/net/yacy/kelondro/blob/Gap.java b/source/net/yacy/kelondro/blob/Gap.java
index 87c733d04..9f46eb85c 100644
--- a/source/net/yacy/kelondro/blob/Gap.java
+++ b/source/net/yacy/kelondro/blob/Gap.java
@@ -86,7 +86,12 @@ public class Gap extends TreeMap<Long, Integer> {
     public int dump(File file) throws IOException {
         File tmp = new File(file.getParentFile(), file.getName() + ".prt");
         Iterator<Map.Entry<Long, Integer>> i = this.entrySet().iterator();
-        DataOutputStream os = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(tmp), 4 * 1024 * 1024));
+        DataOutputStream os;
+        try {
+            os = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(tmp), 4 * 1024 * 1024));
+        } catch (OutOfMemoryError e) {
+            os = new DataOutputStream(new FileOutputStream(tmp));
+        }
         int c = 0;
         Map.Entry<Long, Integer> e;
         while (i.hasNext()) {
diff --git a/source/net/yacy/kelondro/blob/HeapWriter.java b/source/net/yacy/kelondro/blob/HeapWriter.java
index ef6aa756a..5cf0faad0 100644
--- a/source/net/yacy/kelondro/blob/HeapWriter.java
+++ b/source/net/yacy/kelondro/blob/HeapWriter.java
@@ -80,7 +80,12 @@ public final class HeapWriter {
         this.heapFileREADY = readyHeapFile;
         this.keylength = keylength;
         this.index = new HandleMap(keylength, ordering, 8, 100000, readyHeapFile.getAbsolutePath());
-        this.os = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(temporaryHeapFile), outBuffer));
+        try {
+            this.os = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(temporaryHeapFile), outBuffer));
+        } catch (OutOfMemoryError e) {
+            // try this again without buffer
+            this.os = new DataOutputStream(new FileOutputStream(temporaryHeapFile));
+        }
         this.seek = 0;
     }
 
diff --git a/source/net/yacy/kelondro/blob/MapHeap.java b/source/net/yacy/kelondro/blob/MapHeap.java
index d476ab41e..63663343d 100644
--- a/source/net/yacy/kelondro/blob/MapHeap.java
+++ b/source/net/yacy/kelondro/blob/MapHeap.java
@@ -146,12 +146,17 @@ public class MapHeap implements Map<byte[], Map<String, String>> {
         String s = map2string(newMap, "W" + my_SHORT_SECOND_FORMATTER.format() + " ");
         assert s != null;
         byte[] sb = s.getBytes();
-        synchronized (this) {
+        if (cache == null) {
             // write entry
-        	if (blob != null) blob.insert(key, sb);
+            if (blob != null) blob.insert(key, sb);
+        } else {
+            synchronized (this) {
+                // write entry
+                if (blob != null) blob.insert(key, sb);
     
-            // write map to cache
-            if (cache != null) cache.put(key, newMap);
+                // write map to cache
+                cache.put(key, newMap);
+            }
         }
     }
     
diff --git a/source/net/yacy/kelondro/index/HandleMap.java b/source/net/yacy/kelondro/index/HandleMap.java
index 5b221ba69..1f1194752 100644
--- a/source/net/yacy/kelondro/index/HandleMap.java
+++ b/source/net/yacy/kelondro/index/HandleMap.java
@@ -151,7 +151,12 @@ public final class HandleMap implements Iterable<Row.Entry> {
         // everything much faster, but this is not an option here.
         final File tmp = new File(file.getParentFile(), file.getName() + ".prt");
         final Iterator<Row.Entry> i = this.index.rows(true, null);
-        OutputStream os = new BufferedOutputStream(new FileOutputStream(tmp), 4 * 1024 * 1024);
+        OutputStream os;
+        try {
+            os = new BufferedOutputStream(new FileOutputStream(tmp), 4 * 1024 * 1024);
+        } catch (OutOfMemoryError e) {
+            os = new FileOutputStream(tmp);
+        }
         if (file.getName().endsWith(".gz")) os = new GZIPOutputStream(os);
         int c = 0;
         while (i.hasNext()) {
diff --git a/source/net/yacy/kelondro/index/HandleSet.java b/source/net/yacy/kelondro/index/HandleSet.java
index 54eafc230..c9baa41d8 100644
--- a/source/net/yacy/kelondro/index/HandleSet.java
+++ b/source/net/yacy/kelondro/index/HandleSet.java
@@ -112,7 +112,12 @@ public final class HandleSet implements Iterable<byte[]>, Cloneable {
         // otherwise we could just write the byte[] from the in kelondroRowSet which would make
         // everything much faster, but this is not an option here.
         final Iterator<Row.Entry> i = this.index.rows(true, null);
-        final OutputStream os = new BufferedOutputStream(new FileOutputStream(file), 1024 * 1024);
+        OutputStream os;
+        try {
+            os = new BufferedOutputStream(new FileOutputStream(file), 1024 * 1024);
+        } catch (OutOfMemoryError e) {
+            os = new FileOutputStream(file);
+        }
         int c = 0;
         while (i.hasNext()) {
             os.write(i.next().bytes());
diff --git a/source/net/yacy/visualization/CircleTool.java b/source/net/yacy/visualization/CircleTool.java
index d7194d2d7..61a7da43f 100644
--- a/source/net/yacy/visualization/CircleTool.java
+++ b/source/net/yacy/visualization/CircleTool.java
@@ -101,7 +101,7 @@ public class CircleTool {
         return circles[radius - 1];
     }
     
-    public static void circle(final RasterPlotter matrix, final int xc, final int yc, final int radius, int intensity) {
+    public static void circle(final RasterPlotter matrix, final int xc, final int yc, final int radius, final int intensity) {
         if (radius == 0) {
             //matrix.plot(xc, yc, 100);
         } else {
diff --git a/source/net/yacy/visualization/PrintTool.java b/source/net/yacy/visualization/PrintTool.java
index f2a26ebbc..b2f90e7b0 100644
--- a/source/net/yacy/visualization/PrintTool.java
+++ b/source/net/yacy/visualization/PrintTool.java
@@ -111,8 +111,8 @@ public class PrintTool {
     
     private static final int arcDist = 8;
     public static void arcPrint(final RasterPlotter matrix, final int cx, final int cy, final int radius, final int angle, final String message) {
-        final int x = cx + (int) ((radius + 1) * Math.cos(Math.PI * angle / 180));
-        final int y = cy - (int) ((radius + 1) * Math.sin(Math.PI * angle / 180));
+        final int x = cx + (int) ((radius + 1) * Math.cos(RasterPlotter.PI180 * angle));
+        final int y = cy - (int) ((radius + 1) * Math.sin(RasterPlotter.PI180 * angle));
         int yp = y + 3;
         if ((angle > arcDist) && (angle < 180 - arcDist)) yp = y;
         if ((angle > 180 + arcDist) && (angle < 360 - arcDist)) yp = y + 6;
diff --git a/source/net/yacy/visualization/RasterPlotter.java b/source/net/yacy/visualization/RasterPlotter.java
index fba12b523..949a69976 100644
--- a/source/net/yacy/visualization/RasterPlotter.java
+++ b/source/net/yacy/visualization/RasterPlotter.java
@@ -50,6 +50,8 @@ import net.yacy.kelondro.util.MemoryControl;
 
 public class RasterPlotter {
     
+    public static final double PI180 = Math.PI / 180.0d;
+    
     // colors regarding RGB Color Model
     public static final long RED    = 0xFF0000;
     public static final long GREEN  = 0x00FF00;
@@ -211,8 +213,8 @@ public class RasterPlotter {
     
     public void line(
             int Ax, int Ay, final int Bx, final int By,
-            String colorLine, final int intensityLine,
-            String colorDot, final int intensityDot, int dotDist, int dotPos, int dotRadius, boolean dotFilled
+            final String colorLine, final int intensityLine,
+            final String colorDot, final int intensityDot, final int dotDist, final int dotPos, final int dotRadius, final boolean dotFilled
             ) {
         // Bresenham's line drawing algorithm
         int dX = Math.abs(Bx-Ax);
@@ -301,7 +303,7 @@ public class RasterPlotter {
         return grid.getPixel(x, y, c);
     }
 
-    public void dot(final int x, final int y, final int radius, final boolean filled, int intensity) {
+    public void dot(final int x, final int y, final int radius, final boolean filled, final int intensity) {
         if (filled) {
             for (int r = radius; r >= 0; r--) {
                 CircleTool.circle(this, x, y, r, intensity);
@@ -311,16 +313,21 @@ public class RasterPlotter {
         }
     }
     
+    public void arc(final int x, final int y, final int innerRadius, final int outerRadius, final int intensity) {
+        for (int r = innerRadius; r <= outerRadius; r++) {
+            CircleTool.circle(this, x, y, r, intensity);
+        }
+    }
+    
     public void arc(final int x, final int y, final int innerRadius, final int outerRadius, final int fromArc, final int toArc) {
         for (int r = innerRadius; r <= outerRadius; r++) {
             CircleTool.circle(this, x, y, r, fromArc, toArc);
         }
     }
 
-    public void arcLine(final int cx, final int cy, final int innerRadius, final int outerRadius, final int angle,
-            boolean in,
-            String colorLine, String colorDot, int dotDist, int dotPos, int dotRadius, boolean dotFilled) {
-        final double a = Math.PI * ((double) angle) / 180.0;
+    public void arcLine(final int cx, final int cy, final int innerRadius, final int outerRadius, final int angle, final boolean in,
+            final String colorLine, final String colorDot, final int dotDist, final int dotPos, final int dotRadius, final boolean dotFilled) {
+        final double a = PI180 * ((double) angle);
         final double cosa = Math.cos(a);
         final double sina = Math.sin(a);
         final int xi = cx + (int) (innerRadius * cosa);
@@ -344,18 +351,17 @@ public class RasterPlotter {
     }
     
     public void arcDot(final int cx, final int cy, final int arcRadius, final int angle, final int dotRadius) {
-        final double a = Math.PI * ((double) angle) / 180.0;
+        final double a = PI180 * ((double) angle);
         final int x = cx + (int) (arcRadius * Math.cos(a));
         final int y = cy - (int) (arcRadius * Math.sin(a));
         dot(x, y, dotRadius, true, 100);
     }
     
-    public void arcConnect(final int cx, final int cy, final int arcRadius, final int angle1, final int angle2,
-            boolean in,
-            String colorLine, final int intensityLine,
-            String colorDot, final int intensityDot, int dotDist, int dotPos, int dotRadius, boolean dotFilled) {
-        final double a1 = Math.PI * ((double) angle1) / 180.0;
-        final double a2 = Math.PI * ((double) angle2) / 180.0;
+    public void arcConnect(final int cx, final int cy, final int arcRadius, final int angle1, final int angle2, final boolean in,
+            final String colorLine, final int intensityLine,
+            final String colorDot, final int intensityDot, final int dotDist, final int dotPos, final int dotRadius, final boolean dotFilled) {
+        final double a1 = PI180 * ((double) angle1);
+        final double a2 = PI180 * ((double) angle2);
         final int x1 = cx + (int) (arcRadius * Math.cos(a1));
         final int y1 = cy - (int) (arcRadius * Math.sin(a1));
         final int x2 = cx + (int) (arcRadius * Math.cos(a2));
@@ -371,8 +377,17 @@ public class RasterPlotter {
         }
     }
     
-    public void arcArc(final int cx, final int cy, final int arcRadius, final int angle, final int innerRadius, final int outerRadius, final int fromArc, final int toArc) {
-        final double a = Math.PI * ((double) angle) / 180.0;
+    public void arcArc(final int cx, final int cy, final int arcRadius, final int angle,
+            final int innerRadius, final int outerRadius, final int intensity) {
+        final double a = PI180 * ((double) angle);
+        final int x = cx + (int) (arcRadius * Math.cos(a));
+        final int y = cy - (int) (arcRadius * Math.sin(a));
+        arc(x, y, innerRadius, outerRadius, intensity);
+    }
+    
+    public void arcArc(final int cx, final int cy, final int arcRadius, final int angle,
+            final int innerRadius, final int outerRadius, final int fromArc, final int toArc) {
+        final double a = PI180 * ((double) angle);
         final int x = cx + (int) (arcRadius * Math.cos(a));
         final int y = cy - (int) (arcRadius * Math.sin(a));
         arc(x, y, innerRadius, outerRadius, fromArc, toArc);