A Kr*-Rb cold collision apparatus based on atom trap.

A cold collision between atoms and molecules (<1 K) is one of the hot research fields in atomic and molecular physics. At low temperatures, the number of partial waves participating in the collision process decreases dramatically, and quantum phenomena start to emerge. The reaction is often dominated by quantum tunneling, and pronounced resonances can exist on collision cross sections. Here, we report on an apparatus designed for studying cold collisions between metastable noble gas atoms and alkali atoms. Our apparatus features a combined Magneto-Optical-Trap (MOT) and velocity map imaging (VMI) system. The center of a Rb MOT is overlapped with the VMI system. Cold Kr* atoms are launched toward the Rb atoms to induce Kr* + Rb reactions. The collision energy between the two species can be varied from 100 mK to 20 K. With this setup, we are planning to explore the quantum phenomena in Kr* + Rb cold collisions, including the shape resonance and stereodynamics in the reaction.

Structures of the human Wilson disease copper transporter ATP7B.

The P-type ATPase ATP7B exports cytosolic copper and plays an essential role in the regulation of cellular copper homeostasis. Mutants of ATP7B cause Wilson disease (WD), an autosomal recessive disorder of copper metabolism. Here, we present cryoelectron microscopy (cryo-EM) structures of human ATP7B in the E1 state in the apo, the putative copper-bound, and the putative cisplatin-bound forms. In ATP7B, the N-terminal sixth metal-binding domain (MBD6) binds at the cytosolic copper entry site of the transmembrane domain (TMD), facilitating the delivery of copper from the MBD6 to the TMD. The sulfur-containing residues in the TMD of ATP7B mark the copper transport pathway. By comparing structures of the E1 state human ATP7B and E2-Pi state frog ATP7B, we propose the ATP-driving copper transport model of ATP7B. These structures not only advance our understanding of the mechanisms of ATP7B-mediated copper export but can also guide the development of therapeutics for the treatment of WD.

A magnetically enhanced RF discharge source for metastable krypton production.

We describe a high intensity metastable Kr source based on a helical resonator RF discharge. By adding an external B-field to the discharge source, the metastable Kr flux is enhanced. The effect of geometric configuration and magnetic field strength has been studied and optimized experimentally. Compared to the helical resonator discharge source without an external B-field, the new source showed an enhancement factor of 4-5 in producing metastable Kr beams. This improvement has a direct impact on the radio-krypton dating applications as it can increase the atom count rate, resulting in a higher analytical precision.

A Tibetan ice core covering the past 1,300 years radiometrically dated with 39Ar.

Ice cores from alpine glaciers are unique archives of past global and regional climate conditions. However, recovering climate records from these ice cores is often hindered by the lack of a reliable chronology, especially in the age range of 100 to 500 anni (a) for which radiometric dating has not been available so far. We report on radiometric 39Ar dating of an ice core from the Tibetan Plateau and the construction of a chronology covering the past 1,300 a using the obtained 39Ar ages. This is made possible by advances in the analysis of 39Ar using the laser-based detection method atom trap trace analysis, resulting in a twofold increase in the upper age limit of 39Ar dating. By measuring the anthropogenic 85Kr along with 39Ar we quantify and correct modern air contamination, thus removing a major systematic uncertainty of 39Ar dating. Moreover, the 85Kr data for the top part of the ice core provide information on firn processes, including the age difference between the ice and its enclosed gas. This first application of 39Ar and 85Kr to an ice core facilitates further ice cores from nonpolar glaciers to be used for recovering climate records of the Common Era, a period including pronounced anomalies such as the Little Ice Age and the Medieval Warm Period.

Recent Progress in Reconfigurable and Intelligent Metasurfaces: A Comprehensive Review of Tuning Mechanisms, Hardware Designs, and Applications.

Intelligent metasurfaces have gained significant importance in recent years due to their ability to dynamically manipulate electromagnetic (EM) waves. Their multifunctional characteristics, realized by incorporating active elements into the metasurface designs, have huge potential in numerous novel devices and exciting applications. In this article, recent progress in the field of intelligent metasurfaces are reviewed, focusing particularly on tuning mechanisms, hardware designs, and applications. Reconfigurable and programmable metasurfaces, classified as space gradient, time modulated, and space-time modulated metasurfaces, are discussed. Then, reconfigurable intelligent surfaces (RISs) that can alter their wireless environments, and are considered as a promising technology for sixth-generation communication networks, are explored. Next, the recent progress made in simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) that can achieve full-space EM wave control are summarized. Finally, the perspective on the challenges and future directions of intelligent metasurfaces are presented.

Serum Neurofilament Light Chain in Wilson's Disease: A Promising Indicator but Unparallel to Real-Time Treatment Response.

BACKGROUND: Wilson's disease (WD) currently lacks a promising indicator that could reflect neurological impairment and monitor treatment outcome. We aimed to investigate whether serum neurofilament light chain (sNfL) functions as a candidate for disease assessment and treatment monitoring of WD. METHODS: We assessed preclinical and manifested WD patients' sNfL levels compared to controls and analyzed the differences between patients with various clinical symptoms. We then explored the correlation between clinical scales and sNfL levels. And repeated measurements were performed in 34 patients before and after treatment. RESULTS: WD patients with neurological involvement had significantly higher sNfL levels than both hepatic patients and controls. Positive correlations were found between Unified Wilson's Disease Rating Scale scores and sNfL and between semiquantitative magnetic resonance imaging scales and sNfL levels in WD patients. However, in the treatment follow-up analysis, the trend of sNfL before and after treatment disaccorded with clinical response. CONCLUSION: These findings suggest that sNfL levels can be an ideal indicator for the severity of neurological involvement but fail to evaluate change in disease condition after treatment. © 2022 International Parkinson and Movement Disorder Society.

Fast atom-trap analysis of 39Ar with isotope pre-enrichment.

We demonstrate fast analysis of 39Ar/Ar at the 10-16 level using a mass spectrometer for isotope pre-enrichment and an atom trap for counting. An argon gas sample first passes through a dipole mass separator that reduces the dominant isotope 40Ar by two orders of magnitude while preserving both the rare tracer isotope 39Ar and a minor stable isotope 38Ar for control purposes. Measurements of both natural and enriched samples with atom trap trace analysis demonstrate that the 39Ar/38Ar ratios change less than 10%, while the overall count rates of 39Ar are increased by one order of magnitude. By overcoming the analysis-speed bottleneck, this advance will benefit large-scale applications of 39Ar dating in the earth sciences, particularly for mapping ocean circulation.

Linear-polarization metasurface converter with an arbitrary polarization rotating angle.

This paper presents a new design of linear-polarization metasurface converter with arbitrary polarization rotating angle. The linear-polarization conversion is achieved by first separating the linearly polarized incident wave into two orthogonal circularly polarized waves, then adding an additional phase to one of the circularly polarized waves, and finally recombining these two circularly polarized waves into a linearly polarized wave and reflecting it towards free space. A practical unit cell operating at 10 GHz with sandwich structure is applied to realize the linear-polarization metasurface converter, which consists of a top-layer square patch, a middle-layer ground plane, a bottom-layer 90° quadrature hybrid coupler, and two vias connecting the top layer and bottom layer. The proposed linear-polarization metasurface converter is analyzed theoretically and demonstrated by both simulating and experimental results.

Time-coding spread-spectrum reconfigurable intelligent surface for secure wireless communication: theory and experiment.

We present a time-coding reconfigurable intelligent surface (RIS) enabled spread-spectrum secure wireless communication system. The time-coding spread-spectrum RIS is realized by altering the RIS between the two states of a perfect electrical conductor (PEC) and perfect magnetic conductor (PMC), according to a pseudo-random time sequence, respectively. This spectrum spreading function of the time-coding RIS can be simply applied to the secure wireless communication systems, providing a low-cost, easy-implementation encrypting architecture with the two key features of interception prevention and interference suppression. These two features together with the overall spread-spectrum secure wireless communication system are demonstrated by both theoretical analysis and experimental results using a designed 8 × 8 time-coding RIS.

An atom trap system for 39Ar dating with improved precision.

Cosmogenic 39Ar dating is an emerging technique in dating mountain glacier ice, mapping ocean circulation, and tracing groundwater flow. We have realized an atom-trap system for the analysis of the radioactive isotope 39Ar (half-life = 269 years) in environmental samples. The system is capable of analyzing small (1-5 kg) environmental water or ice samples and achieves a count rate of 10 atoms/h for 39Ar at the modern isotopic abundance level of 8 × 10-16. By switching frequently between counting 39Ar atoms and measuring the stable and abundant isotope 38Ar, drift effects in the trapping efficiency are largely suppressed, leading to a more precise measurement of the isotope ratio 39Ar/38Ar. Moreover, cleaning techniques are developed to alleviate cross-sample contamination, reducing the background 39Ar count rate down to <0.5 atoms/h. These advances allow us to determine the 39Ar age in the range of 250-1300 years with precisions of <20%.

Monitoring atmospheric 85Kr by atom counting.

Radioactive 85Kr is a major gaseous fission product emitted into the air by the nuclear fuel reprocessing industry. Measuring atmospheric 85Kr has applications in environmental monitoring, atmospheric transport model validation and dating of environmental water samples, including groundwater, sea water and glacier ice. We present an ultra-sensitive method for fast analysis of atmospheric 85Kr at 10-5 parts per trillion level. This method is based on laser cooling and trapping and is capable of counting individual 85Kr atoms. Measurements at the 3% precision level can be made on krypton extracted from 1L STP of air with a turnaround time of 1.5 h. Moreover, we have realized a system for continuous air sampling over days to weeks. Based on this atom-counting technology and a portable air sample integrator we have realized atmospheric 85Kr baseline monitoring in Hefei, China, for over 20 months. The technological advances presented in this work lay the ground for a global atmospheric 85Kr monitoring network.

Prevalent Pathogenic Variants of ATP7B in Chinese Patients with Wilson's Disease: Geographical Distribution and Founder Effect.

Wilson's disease (WD) is an autosomal recessive disorder caused by ATP7B pathogenic variants. This study aimed to show the geographical distribution and haplotype spectrum of three prevalent pathogenic variants (p.R778L, p.P992L, p.T935M) in mainland Chinese population and clarify whether the founder effect may account for their origins. We firstly summarized the frequency and geographical distribution of p.R778L, p.P992L and p.T935M in 715 WD patients. Then, to construct haplotypes associated with the three variants, Sanger sequencing and microsatellite typing at three dinucleotide-repeat markers (D13S314, D13S301, D13S316) flanking the ATP7B gene were performed in 102 WD families. An obvious regional-specific distribution feature was found in p.T935M. Linkage disequilibrium at the three markers was shown in all the three variants and we found the common haplotypes specific for p.R778L, p.P992L and p.T935M respectively, represented successively by 10-7-7, 10-9-5 and 12-4-8, which all exhibited great significance vs. the control chromosomes (p < 0.01). Meanwhile, haplotypes for the three variants differed from the studies in other regions to some extent. The common haplotypes we found indicate that three prevalent pathogenic variants emerge due to the founder effect. Furthermore, the study contributes to expand our knowledge of the genetic diversity of WD from a cross-regional perspective.

Electronically reconfigurable unit cell for transmit-reflect-arrays in the X-band.

This paper proposes an electronically reconfigurable unit cell for transmit-reflect-arrays in the X-band, which makes it possible to control the reflection or transmission phase independently by combining the mechanisms of reconfigurable transmitarrays and reconfigurable reflectarrays. The fabricated unit cell was characterized in a waveguide simulator. The return loss in the reflection mode and insertion loss in the transmission mode are smaller than 1.8 dB for all states at 10.63 GHz, and a 1-bit phase shift for both modes is achieved within 180° ± 10°. When compared to full-wave electromagnetic simulation results, the proposed unit cell shows good results and is thus verified.

Dual-band multi-bit programmable reflective metasurface unit cell: design and experiment.

Programmable reflective metasurfaces that combine the features of reconfigurable phased array antennas and reflectors are an effective solution for radar and modern communication systems. However, most of the demonstrated active metasurfaces support tunable responses for a specific frequency band. Thus, we propose a programmable metasurface that combines the advantages of multi-bit phase quantization and dual-band operations. To actively control the diverse functions, two PIN diodes are integrated on the radiating element, and these diodes are controlled by the biasing voltage. The unit cell is fabricated, and experimental characterization is performed in the waveguide measurement setup. The proposed design can be applied for imaging and high-capacity wireless communications.

Role for Biochemical Assays and Kayser-Fleischer Rings in Diagnosis of Wilson's Disease.

BACKGROUND & AIMS: Wilson disease is an autosomal recessive disorder that impairs copper homeostasis and is caused by homozygous or compound heterozygous mutations in ATP7B, which encodes a copper-transporting P-type ATPase. Patients have variable clinical manifestations and laboratory test results, resulting in diagnostic dilemmas. We aimed to identify factors associated with symptoms and features of Wilson disease from a large cohort, over 15 years. METHODS: We collected data from 715 patients (529 with symptoms, 146 without symptoms, and 40 uncategorized) and a genetic confirmation of Wilson's disease (mean age of diagnosis, 18.84 years), recruited from 3 hospitals in China from 2004 through 2019. We analyzed clinical data along with serum levels of ceruloplasmin (available from 636 patients), 24-hr urinary copper excretion (collected from 131 patients), Kayser-Fleisher rings (copper accumulation in eyes, with neurologic data from 355 patients), and magnetic resonance imaging (MRI) abnormalities. Differences among the groups were analyzed using 1-way analysis of variance followed by Tukey multiple comparison test. RESULTS: Of the 529 patients with symptoms, 121 had hepatic features, 355 had neurologic features, 28 had osteomuscular features (premature osteoarthritis, skeletal deformities, and pathological bone fractures), and 25 had psychiatric symptoms. Age of onset was significantly younger in patients with hepatic (16.94 ± 1.03 years; P = .0105) or osteomuscular features (13 ± 1.33 years; P = .0001) than patients with neurological features (19.48 ± 0.46 years). Serum levels of ceruloplasmin differed among asymptomatic patients and patients with osteomuscular or neurologic symptoms of Wilson disease. Serum levels of ceruloplasmin ranged from 18.93 mg/L to approximately 120.00 mg/L (quantiles of 0.025 to approximately 0.975). Fifty-one of 131 patients (39%) had urinary copper excretion levels below 100 µg/24 hr; there was significant variation in levels of urinary copper excretion between patients older than 14 years vs 14 years or younger. Of the 355 patients with neurologic features, 244 patients (69%) had abnormal findings from MRI and Kayser-Fleisher rings; only 1 patient with abnormal findings from brain MRI was negative for Kayser-Fleisher rings. CONCLUSIONS: Serum level of ceruloplasmin, 24-hour urinary copper excretion, and Kayser-Fleisher rings can be used to identify patients who might have Wilson disease. Patients with serum levels of ceruloplasmin below 120 mg/L and children with urinary copper excretion above 40 µg should undergo genetic testing for Wilson's disease. Patients with movement disorders and brain MRI abnormalities without Kayser-Fleisher rings are not likely to have Wilson disease.

Clinical features and outcome of Wilson's disease with generalized epilepsy in Chinese patients.

OBJECTIVE: Generalized epilepsy is rarely reported in patients with Wilson disease (WD) and lacks experience in clinical practice. We aim to provide better experience for the diagnosis and treatment for WD patients with epilepsy in the future. METHODS: A retrospective study was performed in 13 Chinese WD patients with generalized epilepsy. Each patient was diagnosed with WD by clinical evaluation and genetic screening. Patients were given small doses of antiepileptic drugs (AEDs), followed by copper-chelation therapy when the seizures stabilized. Clinical manifestations, brain imaging changes, and treatment and outcome after a long-term follow-up were analyzed. RESULTS: Four out of 13 (30.8%) patients stopped taking copper-chelation drugs for more than 1 year before they were admitted for epilepsy. The incidence of epilepsy of WD patients in our cohort is 1.43% (13/910), lower than those (4.5%-5.9%) in other populations. After the attack of epilepsy, frontal lobes were the most common abnormalities (13/13, 100%) in patients, followed by brain stem (8/13, 61.5%) and thalamus (7/13, 53.8%). After a long-term follow-up, brain imaging and clinical manifestations of 8 (8/9, 88.9%) WD patients were significantly improved. CONCLUSIONS: We firstly described WD patients with generalized epilepsy in the Chinese population. WD patients with aggravation of neuropsychiatric symptoms are prone to occur epilepsy; thus, brain MRI should be performed regularly in those patients. Cortical abnormality in brain MRI is a warning sign of epilepsy. Irregular use of copper-chelation drugs and excessive copper deposition in the brain may be the cause of seizures. Long-term standardized treatment for WD can effectively prevent the extensive brain damage and reduce the incidence of epilepsy in WD patients.

Multi-bit dielectric coding metasurface for EM wave manipulation and anomalous reflection.

In this paper, a multi-bit dielectric reflective metasurface is presented for control of electromagnetic (EM) wave scattering and anomalous reflection. The unit cell is designed to act as a 1-, 2-, and 3-bit coding metasurface to attain better control of EM waves. For the 3-bit coding metasurface, the eight digital states have phase responses of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. The top layer of the proposed metasurface consists of high permittivity material to realize a high Q factor. The proposed multi-bit coding metasurface can reflect the incident EM wave to the desired angle with more than 93% power efficiency. For radar cross section reduction applications, the discrete water cycle algorithm is utilized to obtain an optimal coding matrix for the unit cell arrangement, leading to better diffusion-like scattering, dispersion of the EM wave in all directions, and hence minimal specular reflection. The simulation and experimental results verify that the proposed metasurface is a suitable candidate for control of EM wave scattering and anomalous reflection.

Generation of wideband vortex beam with different OAM modes using third-order meta-frequency selective surface.

Orbital angular momentum (OAM) beam generators have attracted tremendous interests recently due to their excellent performance and potential applications in wireless communication. However, the existing transmissive OAM generators suffer from several limitations, such as narrow bandwidth, high profile and low efficiency. In this study, a new wideband third-order meta-frequency selective surface (meta-FSS) for generating focusing vortex beam is developed. The proposed meta-FSS element is designed at X- band with a third-order band-pass filter property, which exhibits the merits of low profile, high transmissivity, and large angular stability. By employing the proposed meta-FSS element, prototypes of OAM generators for + 1 and -2 modes are designed, fabricated, and measured. Experimental results verify the ability of the proposed design to convert an incident left/right-handed circularly polarized (L/RHCP) spherical wave into a transmitted R/LHCP vortex carrying OAM wave from 9.0 GHz to 11.0 GHz with high mode purity. A good agreement is achieved between the experimental and numerical results, which demonstrates that the proposed structure paves the wave for generating desired OAM modes, and provides new possibility for designing novel low-profile wireless communication devices.

Dual Separation of Krypton and Argon from Environmental Samples for Radioisotope Dating.

The noble gas radioisotopes 85Kr, 81Kr, and 39Ar are nearly ideal environmental tracers because of their chemical inertness and simple transport mechanisms. Recent advances in Atom Trap Trace Analysis have enabled measurements of 85Kr and 81Kr using 10-20 kg of water or ice, and 39Ar in only a few kilograms, making these tracers available to be applied in the earth sciences on a large-scale. To meet the resulting increase in demand, we have developed an automated process for the dual separation of krypton and argon from environmental samples based on titanium gettering and gas chromatography. 0.5-4 L STP air samples have been purified, demonstrating purities and recoveries of >90% for krypton and >99% for argon within 90-120 min of processing time. Samples of high methane admixtures, a challenge regularly encountered in groundwater applications, have been purified by exploiting the full potential of titanium gettering at high temperatures (>1000 °C). Samples with 0.4-48 L STP of methane admixture are processed in 2-5 h without compromising purity or recovery. The applicability of the purification system is further demonstrated using actual groundwater samples with carbon dioxide and methane content in the extracted gas up to 16 L STP and 42 L STP, respectively.