Nanocavity tuning and formation controlled by the phase change of sub-micron-square GST patterns on Si photonic crystals.

It has been well established that photonic crystal nanocavities with wavelength sized mode volume enable various integrable photonic devices with extremely small consumption energy and small footprint. In this study, we explore the possibility of non-volatile functionalities employing photonic crystal nanocavities and phase change material, Ge2Sb2Te5 (GST). Recently, non-volatile photonic devices based on GST have attracted significant interest and are expected to enable energy-efficient photonic processing, especially for optical computing. However, the device size and the area of GST in previous studies have been rather large. Here, we propose and fabricate Si photonic crystal nanocavities on which submicron-square GST patterns are selectively loaded. Because of the strong light confinement, extremely small area of GST is sufficient to manipulate the cavity mode. We have succeeded to fabricate 30-nm-thick and several-100nm-square GST blocks patterned at the center of photonic crystal cavity with a high alignment accuracy. We confirmed that the resonant wavelength and Q-factor of cavity modes are controlled by the phase change of GST. Moreover, cavity formation controlled by submicron-sized GST is also demonstrated by GST-loaded photonic-crystal line-defect waveguides. Our approach in which we place sub-micron-sized GST inside a photonic crystal nanocavity is promising for realizing extremely energy-efficient non-volatile integrable photonic devices, such as switches, modulators, memories, and reconfigurable novel devices.

Physical and radiographic features of degenerative retrolisthesis in Japanese female volunteers: an observational cohort study.

Hundred and twenty four females with spondylolisthesis were divided into three groups (A group: anterolisthesis; P group: retrolisthesis; and AP group: antero-retrolisthesis), We reviewed their whole-spine radiographs and measured their standard sagittal parameters, including thoracic kyphosis (TK), pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), and sacral slope (SS). The muscle strengths of the trunk flexor, trunk extensor, iliopsoas, and quadriceps were measured. Health-related quality of life was assessed using the Short Form 36-item Health Survey-physical component summary (SF-36 PCS). PI, SS, and LL-TK of participants in the P group were significantly lower than those in the A and AP groups (PI: P group vs. A group, p < 0.001, P group vs. AP group, p = 0.01), (SS: P group vs. A group, p = 0.001, P group vs. AP group, p = 0.003), (LL-TK: P group vs. A group, p < 0.001, P group vs. AP group, p = 0.049). TK of participants in the P and AP groups was greater than that of those in the A group. (P group vs. A group, p = 0.04, AP group vs. A group, p = 0.0025). The SF-36 PCS score in the P group was lower than that in the A and AP groups. (P group vs. A group, p = 0.004, P group vs. AP group, p = 0.012). The muscle strengths of the trunk flexor and trunk extensor and quadriceps in the P group were lower than those in the A groups. (Trunk flexor: P group vs. A group, p = 0.012), (Trunk extensor: P group vs. A group, p = 0.018), (Quadriceps: P group vs. A group, p = 0.011). In conclusion, female participants with degenerative retrolisthesis had a smaller PI and SS and a larger TK, along with decreased physical function and QoL scores than those with anterolisthesis.

Examination of the changes in lower extremities related to progression of adult spinal deformity: a longitudinal study of over 22 years.

This longitudinal observational study investigated the relationship between changes in spinal sagittal alignment and changes in lower extremity coronal alignment. A total of 58 female volunteers who visited our institution at least twice during the 1992 to 1997 and 2015 to 2019 periods were investigated. We reviewed whole-spine radiographs and lower extremity radiographs and measured standard spinal sagittal parameters including pelvic incidence [PI], lumbar lordosis [LL], pelvic tilt [PT], sacral slope [SS] and sagittal vertical axis [SVA], and coronal lower extremity parameters including femorotibial angle (FTA), hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA) and mechanical lateral distal tibial angle (mLDTA). Lumbar spondylosis and knee osteoarthritis were assessed using the Kellgren-Lawrence (KL) grading system at baseline and at final follow-up. We investigated the correlation between changes in spinal sagittal alignment and lower extremity alignment and changes in lumbar spondylosis. The mean age [standard deviation (SD)] was 48.3 (6.3) years at first visit and 70.2 (6.3) years at final follow-up. There was a correlation between changes in PI-LL and FTA (R = 0.449, P < 0.001) and between PI-LL and HKA (R = 0.412, P = 0.001). There was a correlation between changes in lumbar spondylosis at L3/4 (R = 0.383, P = 0.004) and L4/5 (R = 0.333, P = 0.012) and the knee joints. Changes in lumbar spondylosis at L3/4 and L4/5 were related to changes in KOA. Successful management of ASD must include evaluation of the state of lower extremity alignment, not only in the sagittal phase, but also the coronal phase.

Adult spinal deformity and its relationship with height loss: a 34-year longitudinal cohort study.

BACKGROUND: Age-related height loss is a normal physical change that occurs in all individuals over 50 years of age. Although many epidemiological studies on height loss have been conducted worldwide, none have been long-term longitudinal epidemiological studies spanning over 30 years. This study was designed to investigate changes in adult spinal deformity and examine the relationship between adult spinal deformity and height loss. METHODS: Fifty-three local healthy subjects (32 men, 21 women) from Furano, Hokkaido, Japan, volunteered for this longitudinal cohort study. Their heights were measured in 1983 and again in 2017. Spino-pelvic parameters were compared between measurements obtained in 1983 and 2017. Individuals with height loss were then divided into two groups, those with degenerative spondylosis and those with degenerative lumbar scoliosis, and different characteristics were compared between the two groups. RESULTS: The mean age of the subjects was 44.4 (31-55) years at baseline and 78.6 (65-89) years at the final follow-up. The mean height was 157.4 cm at baseline and 153.6 cm at the final follow-up, with a mean height loss of 3.8 cm over 34.2 years. All parameters except for thoracic kyphosis were significantly different between measurements taken in 1983 and 2017 (p < 0.05). Height loss in both sexes was related to changes in pelvic parameters including pelvic incidence-lumbar lordosis (R = 0.460 p = 0.008 in men, R = 0.553 p = 0.012 in women), pelvic tilt (R = 0.374 p = 0.035 in men, R = 0.540 p = 0.014 in women), and sagittal vertical axis (R = 0.535 p = 0.002 in men, R = 0.527 p = 0.017 in women). Greater height loss was more commonly seen in women (p = 0.001) and in patients with degenerative lumbar scoliosis (p = 0.02). CONCLUSIONS: This longitudinal study revealed that height loss is more commonly observed in women and is associated with adult spinal deformity and degenerative lumbar scoliosis. Height loss is a normal physical change with aging, but excessive height loss is due to spinal kyphosis and scoliosis leading to spinal malalignment. Our findings suggest that height loss might be an early physical symptom for spinal malalignment.

Reconfigurable nanocavity formation in graphene-loaded Si photonic crystal structures.

We propose and numerically demonstrate that a reconfigurable nanocavity can be created in a graphene-loaded Si photonic crystal waveguide. The cavity formation is caused by the local mode-gap modulation induced by electrostatic gate-tuning of graphene. Although most recent graphene photonic devices are based on a change in the imaginary part of the refractive index, here we make use of a change in the real part of the refractive index for gated graphene. We clarify that nanocavities can be formed in two different cases, red-shifted and blue-shifted tunings. These novel formation mechanisms enable us to create and annihilate a nanocavity in a reconfigurable way by varying the gate voltage, which is promising for novel control in photonic processing.

Adult spinal deformity and its relationship with hip range of motion: a cohort study of community-dwelling females.

BACKGROUND CONTEXT: Adult spinal deformity affects lower extremity alignment with compensation in joint range of motion (ROM) and alignment of the hip. PURPOSE: To investigate the relationship between sagittal spinopelvic alignment and the ROM of the hip joint and the femoral oblique angle (FOA). STUDY DESIGN: Cross-sectional, observational cohort study of community-dwelling Japanese women. METHODS: The study group included 158 women, enrolled in our ongoing prospective cohort study, with upright spine radiographs and physical measurements obtained for all participants. Radiographic spinopelvic parameters included measurement of thoracic kyphosis, lumbar lordosis (LL), sagittal vertical axis (SVA), sacral slope, pelvic incidence, and pelvic tilt (PT). FOA parameters were measured on hip radiographs and hip ROM included external and internal rotation and extension. The association between spinopelvic parameters, the FOA, and hip joint ROM was evaluated using Spearman's correlation analysis. RESULTS: External rotation of the hip was correlated with LL (R=0.179, p=.024), PT (R=-0.273, p=.001) and SVA (R=-0.215, p=.007), with the FOA being correlated with the SVA (R=0.502, p<.001). CONCLUSIONS: The decrease in hip external rotation with adult spinal deformity might reflect a structural modification in spinopelvic alignment. An increase in FOA was associated with an increase in SVA, indicative of a sagittal malalignment in the decompensated phase of adult spinal deformity.

Direct observation of ultrafast many-body electron dynamics in an ultracold Rydberg gas.

Many-body correlations govern a variety of important quantum phenomena such as the emergence of superconductivity and magnetism. Understanding quantum many-body systems is thus one of the central goals of modern sciences. Here we demonstrate an experimental approach towards this goal by utilizing an ultracold Rydberg gas generated with a broadband picosecond laser pulse. We follow the ultrafast evolution of its electronic coherence by time-domain Ramsey interferometry with attosecond precision. The observed electronic coherence shows an ultrafast oscillation with a period of 1 femtosecond, whose phase shift on the attosecond timescale is consistent with many-body correlations among Rydberg atoms beyond mean-field approximations. This coherent and ultrafast many-body dynamics is actively controlled by tuning the orbital size and population of the Rydberg state, as well as the mean atomic distance. Our approach will offer a versatile platform to observe and manipulate non-equilibrium dynamics of quantum many-body systems on the ultrafast timescale.

Clinical, physical, and radiographic analyses of lumbar degenerative kyphosis and spondylolisthesis among community-based cohort.

PURPOSE: To investigate longitudinal radiographic changes, and physical characteristics of lumbar degenerative kyphosis (LDK) and spondylolisthesis (DS). METHODS: Two-hundred eighty nine community-based female subjects were recruited from population register and studied longitudinally for a mean 12.3 years. Upright entire spine radiographs were used to evaluate spinopelvic parameters, including lumbar lordosis (LL), pelvic incidence (PI), and vertebral slip (% slip). Physical measurements included lumbar range of motion (ROM), isometric trunk muscle strength, and photometric gait posture using change in trunk inclination angle (dTIA). RESULTS: Subjects' mean age (standard deviation: SD) was 56.9 (10.0) years at baseline and 68.5 (9.2) years at the final follow-up. Among 202 subjects who could perform instructed physical measurements, DS, defined as more than 5 % slip, was found in 50 subjects (24.8 %), and LDK, defined as LL of less than 1SD of mean value (<24.4°), was found in 24 subjects (11.9 %). DS subjects showed a significant weakness in trunk flexor strength (normal 282.5 ± 73.0 N vs. DS 245.5 ± 75.5 N, p = 0.0219), and LDK subjects showed significant differences in: trunk extensor strength (normal 493.4 ± 172.8 N vs. LDK 386.3 ± 167.6 N, p = 0.0066), ROM, and dTIA (normal 3.5° ± 2.7° vs. LDK 7.6° ± 4.8°, p < 0.0001). PI was significantly larger in DS and smaller in LDK than normal subjects (normal 53.8° ± 9.9° vs. DS 58.2° ± 10.6°, p = 0.0111; normal vs. LDK 48.4° ± 9.2°, p = 0.0191). CONCLUSIONS: Current study showed that DS was associated with reduced trunk flexor strength, which might increase pelvic anteversion, and LDK was associated with reduced extensor strength, ROM, and ambulatory kyphosis. Physical characteristics should be evaluated for the successful management of adult spinal deformity.

Ultrafast Fourier transform with a femtosecond-laser-driven molecule.

Wave functions of electrically neutral systems can be used as information carriers to replace real charges in the present Si-based circuit, whose further integration will result in a possible disaster where current leakage is unavoidable with insulators thinned to atomic levels. We have experimentally demonstrated a new logic gate based on the temporal evolution of a wave function. An optically tailored vibrational wave packet in the iodine molecule implements four- and eight-element discrete Fourier transform with arbitrary real and imaginary inputs. The evolution time is 145 fs, which is shorter than the typical clock period of the current fastest Si-based computers by 3 orders of magnitudes.

Wave packet interferometry with attosecond precision and picometric structure.

Wave packet (WP) interferometry is applied to the vibrational WPs of the iodine molecule. Interference fringes of quantum waves weave highly regular space-time images called "quantum carpets." The structure of the carpet has picometre and femtosecond resolutions, and changes drastically depending on the amplitudes and phases of the vibrational eigenstates composing the WP. In this review, we focus on the situation where quantum carpets are created by two counter-propagating nuclear vibrational WPs. Such WPs can be prepared with either a single or double femtosecond (fs) laser pulse. In the single pulse scheme, the relevant situation appears around the half revival time. Similar situations can be generated with a pair of fs laser pulses whose relative phase is stabilized on the attosecond time scale. In the latter case we can design the quantum carpet by controlling the timing between the phase-locked pulses. We demonstrate this carpet design and visualize the designed carpets by the fs pump-probe measurements, tuning the probe wavelength to resolve the WP density-distribution along the internuclear axis with ~3 pm spatial resolution and ~100 fs temporal resolution.

Actively tailored spatiotemporal images of quantum interference on the picometer and femtosecond scales.

Interference fringes of quantum waves weave highly regular space-time images, which could be seen in various wave systems such as wave packets in atoms and molecules, Bose-Einstein condensates, and fermions in a box potential. We have experimentally designed and visualized spatiotemporal images of dynamical quantum interferences of two counterpropagating nuclear wave packets in the iodine molecule; the wave packets are generated with a pair of femtosecond laser pulses whose relative phase is locked within the attosecond time scale. The design of the image has picometer and femtosecond resolutions, and changes drastically as we change the relative phase of the laser pulses, providing a direct spatiotemporal control of quantum interferences.

Real-time observation of phase-controlled molecular wave-packet interference.

The quantum interference of two molecular wave packets has been precisely controlled in the B electronic state of the I2 molecule by using a pair of fs laser pulses whose relative phase is locked within the attosecond time scale and its real-time evolution has been observed by another fs laser pulse. It is clearly observed that the temporal evolution changes drastically as a function of the relative phase between the locked pulses, allowing us to read both amplitude and phase information stored in the wave functions of the molecular ensemble.

Implementation of quantum gate operations in molecules with weak laser fields.

We numerically propose a way to perform quantum computations by combining an ensemble of molecular states and weak laser pulses. A logical input state is expressed as a superposition state (a wave packet) of molecular states, which is initially prepared by a designed femtosecond laser pulse. The free propagation of the wave packet for a specified time interval leads to the specified change in the relative phases among the molecular basis states, which corresponds to a computational result. The computational results are retrieved by means of quantum interferometry. Numerical tests are implemented in the vibrational states of the B state of I2 employing controlled-NOT gate, and 2 and 3 qubits Fourier transforms. All the steps involved in the computational scheme, i.e., the initial preparation, gate operation, and detection steps, are achieved with extremely high precision.

Visualizing picometric quantum ripples of ultrafast wave-packet interference.

Interference fringes in vibrating molecules are a signature of quantum mechanics, but are often so short-lived and closely spaced that they elude visualization. We have experimentally visualized dynamical quantum interferences, which appear and disappear in less than 100 femtoseconds in the iodine molecule synchronously with the periodic crossing of two counterpropagating nuclear wave packets. The obtained images have picometer and femtosecond spatiotemporal resolution, representing a detailed picture of the quantum interference.