diff --git a/jupyter_core/application.py b/jupyter_core/application.py
index 7b65f49..e55a657 100644
--- a/jupyter_core/application.py
+++ b/jupyter_core/application.py
@@ -83,7 +83,7 @@ def _log_level_default(self) -> int:
     def _jupyter_path_default(self) -> list[str]:
         return jupyter_path()
 
-    config_dir: str | Unicode = Unicode()
+    config_dir = Unicode()
 
     def _config_dir_default(self) -> str:
         return jupyter_config_dir()
@@ -96,41 +96,39 @@ def config_file_paths(self) -> list[str]:
             path.insert(0, self.config_dir)
         return path
 
-    data_dir: str | Unicode = Unicode()
+    data_dir = Unicode()
 
     def _data_dir_default(self) -> str:
         d = jupyter_data_dir()
         ensure_dir_exists(d, mode=0o700)
         return d
 
-    runtime_dir: str | Unicode = Unicode()
+    runtime_dir = Unicode()
 
     def _runtime_dir_default(self) -> str:
         rd = jupyter_runtime_dir()
         ensure_dir_exists(rd, mode=0o700)
         return rd
 
-    @observe("runtime_dir")  # type:ignore[misc]
+    @observe("runtime_dir")
     def _runtime_dir_changed(self, change: t.Any) -> None:
         ensure_dir_exists(change["new"], mode=0o700)
 
-    generate_config: bool | Bool = Bool(
-        False, config=True, help="""Generate default config file."""
-    )
+    generate_config = Bool(False, config=True, help="""Generate default config file.""")
 
-    config_file_name: str | Unicode = Unicode(config=True, help="Specify a config file to load.")
+    config_file_name = Unicode(config=True, help="Specify a config file to load.")
 
     def _config_file_name_default(self) -> str:
         if not self.name:
             return ""
         return self.name.replace("-", "_") + "_config"
 
-    config_file: str | Unicode = Unicode(
+    config_file = Unicode(
         config=True,
         help="""Full path of a config file.""",
     )
 
-    answer_yes: bool | Bool = Bool(False, config=True, help="""Answer yes to any prompts.""")
+    answer_yes = Bool(False, config=True, help="""Answer yes to any prompts.""")
 
     def write_default_config(self) -> None:
         """Write our default config to a .py config file"""
diff --git a/jupyter_core/utils/__init__.py b/jupyter_core/utils/__init__.py
index 6e26c17..0c043d4 100644
--- a/jupyter_core/utils/__init__.py
+++ b/jupyter_core/utils/__init__.py
@@ -127,7 +127,6 @@ def run(self, coro: Any) -> Any:
 
 
 _runner_map: dict[str, _TaskRunner] = {}
-_loop_map: dict[str, asyncio.AbstractEventLoop] = {}
 
 
 def run_sync(coro: Callable[..., Awaitable[T]]) -> Callable[..., T]:
@@ -161,9 +160,11 @@ def wrapped(*args: Any, **kwargs: Any) -> Any:
             pass
 
         # Run the loop for this thread.
-        if name not in _loop_map:
-            _loop_map[name] = asyncio.new_event_loop()
-        loop = _loop_map[name]
+        try:
+            loop = asyncio.get_event_loop()
+        except RuntimeError:
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
         return loop.run_until_complete(inner)
 
     wrapped.__doc__ = coro.__doc__
diff --git a/pyproject.toml b/pyproject.toml
index 6deba32..ae05147 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -88,7 +88,7 @@ nowarn = "test -W default {args}"
 
 [tool.hatch.envs.typing]
 features = ["test"]
-dependencies = ["mypy>=1.5.1"]
+dependencies = ["mypy>=1.5.1", "traitlets>=5.10.1"]
 [tool.hatch.envs.typing.scripts]
 test = "mypy --install-types --non-interactive {args}"