Precise spectroscopy of 167Er:Y2SiO5 based on laser frequency stabilization using a fiber laser comb

Precise spectroscopy of the hyperfine level system of ¹⁶⁷Er-doped Y₂SiO₅ was achieved in the frequency domain. By using an optical frequency comb to stabilize the light source frequency to an accuracy on the order of hertz on a long-term scale, Allan deviation < 10 Hz was achieved for an integration time of 180 s. As a result, spectral hole-burning experiments yielded a more accurate hole spectrum with a narrow homogeneous linewidth. The method opens the way to the straightforward exploration of relaxation mechanisms in the frequency domain by simple steady-state measurements.

Preferential changes of skeletal muscle echogenicity in myotonic dystrophy type 1

BACKGROUND AND PURPOSE

In myotonic dystrophy type 1 (DM1), weakness of distal limb muscles affects quality of life. Non-invasive evaluation of muscular involvement by muscle sonography could be useful for characterizing muscle-specific involvement.

METHODS

Sonography of the lower leg and forearm was performed in 19 patients with DM1 and 10 control subjects. The mean echo intensities (EIs) of seven limb muscles were obtained by computer-assisted histogram analysis and compared within DM1 according to the overall clinical severity.

RESULTS

The EIs of the muscles were significantly higher in DM1 than in the controls (P < 0.01), except for the soleus (P = 0.4). Comparison of adjacent muscles showed the following: (i) greater EIs in flexor digitorum profundus than flexor carpi ulnaris (P < 0.01) and flexor digitorum superficialis (P = 0.02), and (ii) greater EIs in the medial head of the gastrocnemius than the soleus (P < 0.00001). In a subgroup analysis of DM1 according to the modified Rankin Scale (mRS), the more severe subgroup (mRS = 4-5) had lower mean EIs than the less severe subgroup (mRS from 1-3) (P = 0.01) in the flexor digitorum superficialis but not in other muscles.

CONCLUSIONS

Preferential high echogenicity in the medial gastrocnemius and deep finger flexors is suggestive of DM1. Muscle echogenicity is not generally related to functional dysfunction in DM1.

Amyotrophic lateral sclerosis and motor neuron syndromes in Asia

While the past 2 decades have witnessed an increasing understanding of amyotrophic lateral sclerosis (ALS) arising from East Asia, particularly Japan, South Korea, Taiwan and China, knowledge of ALS throughout the whole of Asia remains limited. Asia represents >50% of the world population, making it host to the largest patient cohort of ALS. Furthermore, Asia represents a diverse population in terms of ethnic, social and cultural backgrounds. In this review, an overview is presented that covers what is currently known of ALS in Asia from basic epidemiology and genetic influences, through to disease characteristics including atypical phenotypes which manifest a predilection for Asians. With the recent establishment of the Pan-Asian Consortium for Treatment and Research in ALS to facilitate collaborations between clinicians and researchers across the region, it is anticipated that Asia and the Pacific will contribute to unravelling the uncertainties in ALS.