Search

BackgroundGene therapy is gradually becoming recognized as a possibly curative therapeutic strategy for transfusion-dependent β-thalassemia (TDT). Gene therapy addresses the problem of donor scarcity through the application of autologous hematopoietic stem cells (HSCs), which also can reduce the risks that accompany allogeneic HSC transplantation. When using gene addition strategy, lentiviral vector is critical for the efficacy and safety of β-thalassemia gene therapy. In our preclinical studies, LentiHBBT87Qvector with optimized backbone was developed to efficiently restore β–globin expression in HSCs-derived erythroblasts of TDT patients with minimal risk of tumorigenesis. Here, we presented the clinical trial results of gene therapy using LentiHBBT87Qvector in two TDT patients.MethodIn an ongoing phase 1/2 trial (NCT05745532), auto-HSCs were mobilized from two TDT patients, and then transduced with LentiHBBT87Qvector. The gene-modified auto-HSCs is called HGI-001 injection. After four-day consecutive myeloablative conditioning, these two patients were administrated with HGI-001 injection via intravenous infusion. Medical examinations were performed in the transplantation unit to monitor patients’ status till the patients were clinically stable. Then, 24-month following-up visits are conducted to assess the safety and efficacy of HGI-001 injection. The safety endpoints of this clinical study include the incident and severity of adverse events (AEs); transplant-related mortality or disability events within 100 days post drug product infusion; vector-related replication competent lentivirus (RCL) and clonal variations containing specific viral integration sites; overall survival during this clinical trial. The major efficacy endpoint is the percentage of subjects with average vector copy number (VCN) in peripheral blood mononuclear cells (PBMCs) >0.1, and average expression of exogenous HbAT87Q>2.0g/dL at the 24thmonth after reinfusion of HGI-001 injectionResultsThe rapid neutrophil and platelet engraftment successfully happened after reinfusion of HGI-001 injection. The two patients with non-β0/β0genotype have been transfusion-independent for 24 months and 21 months post-treatment. At the last visit, the levels of HbAT87Qare 7.3 and 6.9g/dL, and the levels of total hemoglobin are 9.8 and 10.1 g/dL. After the two subjects stopped transfusions, the iron overload has been alleviated without iron chelation treatment. Most AEs are myeloablative conditioning related, and can be controlled through clinically standard therapeutic managements. No clone dominance related to vector integration nor RCL has been observed.ConclusionGene therapy with optimized LentiHBBT87Qvector (HGI-001 injection) assist two TDT patients become transfusion-independent without serious adverse events related to the product.

This is a study of the coordination model of consumer information sharing in the tourism supply chain with e-commerce platforms as the core. On the basis of considering the risks, a game theory is used to explore the information sharing effort level and the output profit of the tourism supply chain under both, centralized decision-making and decentralized decision-making. Finally, numerical simulation is used to verify the model and put forward a method of coordination for all parties in the tourism supply chain to achieve maximum profit.

The agriculture field is a fundamental industry which supports the rapid development of the nation’s economy. However, credit constraints faced by farmers have restricted the modernization in the agricultural industry. The agricultural supply chain finance is effective in promoting rural industrial revitalization and agricultural modernization, which is of great significance to the transformation and development of rural economy and agriculture in China. In this paper, the financial coordination model in agricultural supply chain is constructed, and the income distribution model of Shapley value method is introduced. The results showed that the agricultural supply chain finance can significantly improve the income of the participants in the agricultural industrial chain and verify the economic feasibility of agricultural supply chain finance.

Beyond diffraction limit, multitrapping of nanoparticles is important in numerous scientific fields, including biophysics, materials science and quantum optics. Here, we demonstrate the 3-dimensional (3D) shell-like structure of optical trapping well induced by nonlinear optical effects in the femtosecond Gaussian beam trapping for the first time. Under the joint action of gradient force, scattering force and nonlinear trapping force, the gold nanoparticles can be stably trapped in some special positions, or hop between the trap positions along a route within the 3D shell. The separation between the trap positions can be adjusted by laser power and numerical aperture (NA) of the trapping objective lens. With a high NA lens, we achieved dual traps with less than 100 nm separation without utilizing complicated optical systems or any on-chip nanostructures. These curious findings will greatly extend and deepen our understanding of optical trapping based on nonlinear interaction and generate novel applications in various fields, such as microfabrication/nanofabrication, sensing and novel micromanipulations.

Based on principal-agent theory, this paper establishes an incentive contract mechanism between government and NPO under asymmetric information, and analyzes the impact of absolute risk aversion and output level on the expected utility of government, NPO and society. Research shows that risk aversion is negatively correlated with the expected utility of government, NPO and society. The output coefficient is positively correlated with the expected utility of government, NPO and society. Reducing absolute risk aversion, increasing output coefficient and increasing government incentives can effectively motivate NPO to actively participate in social rescue activities.

The ability of light beams to rotate nano-objects has important applications in optical micromachines and biotechnology. However, due to the diffraction limit, it is challenging to rotate nanoparticles at subwavelength scale. Here, we propose a method to obtain controlled fast orbital rotation (i.e., circumgyration) at deep subwavelength scale, based on the nonlinear optical effect rather than sub-diffraction focusing. We experimentally demonstrate rotation of metallic nanoparticles with orbital radius of 71 nm, to our knowledge, the smallest orbital radius obtained by optical trapping thus far. The circumgyration frequency of particles in water can be more than 1 kHz. In addition, we use a femtosecond pulsed Gaussian beam rather than vortex beams in the experiment. Our study provides paradigms for nanoparticle manipulation beyond the diffraction limit, which will not only push toward possible applications in optically driven nanomachines, but also spur more fascinating research in nano-rheology, micro-fluid mechanics and biological applications at the nanoscale., It has been challenging to rotate nanoparticles orbitally via optical trapping beyond the diffraction limit. Here, the authors take advantage of the nonlinear optical effect and demonstrate fast and controlled orbital rotation at subwavelength scale with a femtosecond pulsed Gaussian beam.

All-optical photonic crystal diodes based on the Fano resonance of nonlinear defects are studied. The diodes can achieve nonreciprocal transmission ratios of 31.7 dB and 33.9 dB at working wavelengths of 1534.83 nm and 1536.02 nm, respectively. The function of two defects’ coupling to the performance of unidirectional light transmission is also analyzed. When two Fano cavities are cascaded to form a two-branch-channel diode, unidirectional light propagation at 1536.88, 1538.76, 1612.80, and 1616.78 nm wavelengths is achieved along two opposite forward directions, and the nonreciprocal transmission ratios are 36.5, 30.3, 23.9, and 19.6 dB, respectively.

The efficacy of submicron chitosan dispersions (SCD) on Alternaria alternata rot of the ‘Lingwu changzao’ jujube (Zizyphus jujuba Mill. cv. Lingwu changzao) fruit and possible mechanisms involved were investigated in this study. When jujube fruit at the preharvest stage were sprayed twice with SCD (10 mg/ml) water solution and then natural infections were allowed to develop, there was a significant reduction in disease incidence and lesion index compared to control fruit during storage period, and similar results were obtained from postharvest fruit inoculated with the Alternaria rot pathogen. Scanning electron microscopy of the pathogen revealed that hyphae and spores were damaged and deformed when growing on the surface of fruit pretreated with SCD or CHO. The slowed softening of jujube fruit resulted from the protopectin content increasing compared with the control. Furthermore, SCD sprays inhibited cell wall hydrolysing enzymes, pectinase activity was decreased, and the increase in cellulase activity was postponed (from 30 days to 45 days).It was concluded that preharvest application of SCD was a more effective alternative to conventional chitosan for preventing postharvest from Alternaria rot of ‘Lingwu changzao’ jujube fruit.

Circular dichroism (CD), as one of the most representative chiroptical effects, provides a simple strategy for the detection and characterization of the molecular chirality. The enhancement and sign reversal of CD are of great importance for its practical applications in chiral bio-sensing, chirality switching and optical filtering, etc. Here, we realize considerable adjustments and the sign reversal of CD in quasi-three-dimensional (quasi-3D) combined Archimedean spiral nanostructures. With special local and lattice configurations, the nanostructures have both right-handed and left-handed geometric chirality, which are designed based on the proximity effect of stencil lithography. We find that the CD response of the nanostructures becomes obvious once its height exceeds 200 nm and can be adjusted by the further increase of the height or the change of the blade spacing of the nanostructures. The CD reversal is achieved by utilizing the competition of two chiral centers when the height or blade spacing exceeds a critical value. Further analysis of the scattering power of multipole moments reveals that the CD modulation is determined by both magnetic dipole moment and electric quadrupole moment. Benefiting from the highly sensitive CD response to the height, the extreme sign reversal of CD is achieved when a sub-10-nm ultrathin medium layer is anchored on the surface of the nanostructures, which provides a promising strategy for ultra-sensitive chiral bio-sensing.

Tunable/reconfigurable metasurfaces that can actively control electromagnetic waves upon external stimuli are of great importance for practical applications of metasurfaces. Here, we demonstrate a reconfigurable nano-kirigami metasurface driven by pneumatic pressure operating in the near-infrared wavelength region. The metasurfaces consist of combined Archimedean spirals and are fabricated in a free-standing gold/silicon nitride nanofilm by employing focused ion beam (FIB) lithography. The deformable spirals are instantly transformed from two dimensional (2D) to three-dimensional (3D) by the FIB-based nano-kirigami process. The 2D–to–3D transformation induces a dramatic irreversible change of the plasmonic quadruple modes and results in significant modulation in reflection by 137%. The suspended porous nano-kirigami metasurface is further integrated with an optofluidics device, with which the optical resonance is reversibly modulated by the pneumatic pressure. This work provides a strategy for tunable/reconfigurable metasurfaces, which are useful to build a promising lab-on-a-chip platform for microfluidics, biological diagnostics, chemical sensing, and pressure monitoring.

In the 40 years since the reform and opening up, China's logistics industry has made great progress, but there is still the problem of uneven development in various provinces and regions. This paper selects three first-level indicators and 18 second-level indicators to establish an evaluation index system for the development level of the logistics industry. The three primary indicators include infrastructure indicators, scale indicators and external environmental indicators. By using the grey relational analysis and Entropy weight method to evaluate China's logistics industry development level, and compare logistics industry development level of provinces and regions. It is concluded that the cause of the provinces and regional logistics industry development level is uneven. Finally, according to the actual situation provide suggestions for the development of logistics industry in future.

The combination of graphene and a silicon photonic crystal cavity provides an ideal structure for realizing sensitive all-optical modulation. In this paper, an all-optical tuning of a graphene-cladded photonic crystal cavity is demonstrated. A 3.5 nm resonance wavelength shift and a 20% quality factor change are observed as a 1064 nm continuous-wave control laser is focused on the cavity. The resonance wavelength shift is nearly 2 times that realized with electrical modulation and can be further improved with increasing laser power. Meanwhile, it is found that the laser power to reach the saturation absorption state of graphene is nearly 2 orders of magnitude lower than that for monolayer graphene on silica. The experimental results are attributed to optically induced transparency and hot carrier effects. This study opens up a promising way to construct a sensitive all-optical modulator, which is a necessary device in an all-optical integrated circuit, by using a graphene-cladded photonic crystal cavity.

The inhibitory effect of yeast Pichia membranaefaciens on black spot decay of postharvest broccoli, caused by Alternaria alternata (Fr.) Keissler, was investigated and possible mechanisms were explored in both in vitro and in vivo experiments. There was a positive correlation between the concentration of yeast cells and reduction of hyphal growth or spore germination from 1 × 104 to 1 × 108 cells/ml. When the pathogen and yeast cells were co-cultured at 1 × 108 yeast cells/ml, swollen pathogen hyphae, inner substance leakage, and curved or fragmented spore germ tubes were observed. In postharvest tests, disease incidence and lesion diameter were significantly reduced at 1 × 108 yeast cells/ml at 10 ± 1 °C; the activities of cellulase and pectinase excreted by the pathogen were reduced and the chitinase activity in the pathogen-host system was increased significantly. Taken together, the results suggested that pathogen infection of wounds was inhibited, and the hydrolytic enzymes appeared to contribute to the control mechanism of P. membranaefaciens by inhibiting hyphal growth or spore germination.

Acoustic waves can act as tweezers to trap and rotate particles without contact, which have promising application in the manipulation of tissues and living cells. Here, we report a realization of acoustic tweezers and motor. The device is fabricated on a silicon chip scaled to manipulate living cells. The silicon chip transfers incident plane ultrasonic waves into a vortex beam, which traps particles in the center of the device and exerts torque on the particles simultaneously. As an illustration, we put living shrimp eggs inside the acoustic vortex and observe the acoustic driving rotation. The rotation frequency of the shrimp egg can be easily controlled, and its relationship between driving voltage and the egg size is established. We anticipate that the acoustic tweezers and motor can find widespread applications in cell manipulation, cell screening, and micro actuator in the future.

A transmissive terahertz (THz) metasurface consisting of subwavelength silicon post resonators is proposed, and the performances of high efficiency (over 94%) and full phase shift ( ∼ 2 π ) are achieved through structural design. Based on the predominant dipole resonance characteristic of incident THz wave with the resonator elements, the hyperbolic THz wave phase profiles are generated, and the THz flat lens with a focal length of 1.80 mm supporting the y-polarized wave at 1.0 THz is achieved, whose focal spots along x and y directions of the focal plane are 0.66 λ and 0.44 λ , respectively. Due to the equal phase retardation in two arbitrary perpendicular directions of the post resonators, the lens also has the advantage of polarization-insensitive.

Bacillus coagulans 2-6 is an excellent producer of optically pure l -lactic acid. However, little is known about the mechanism of synthesis of the highly optically pure l -lactic acid produced by this strain. Three enzymes responsible for lactic acid production—NAD-dependent l -lactate dehydrogenase ( l -nLDH; encoded by ldhL ), NAD-dependent d -lactate dehydrogenase ( d -nLDH; encoded by ldhD ), and glycolate oxidase (GOX)—were systematically investigated in order to study the relationship between these enzymes and the optical purity of lactic acid. Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 (a d -lactic acid producer) and Lactobacillus plantarum subsp. plantarum DSM 20174 (a dl -lactic acid producer) were also examined in this study as comparative strains, in addition to B. coagulans . The specific activities of key enzymes for lactic acid production in the three strains were characterized in vivo and in vitro , and the levels of transcription of the ldhL , ldhD , and GOX genes during fermentation were also analyzed. The catalytic activities of l -nLDH and d -nLDH were different in l -, d -, and dl -lactic acid producers. Only l -nLDH activity was detected in B. coagulans 2-6 under native conditions, and the level of transcription of ldhL in B. coagulans 2-6 was much higher than that of ldhD or the GOX gene at all growth phases. However, for the two Lactobacillus strains used in this study, ldhD transcription levels were higher than those of ldhL . The high catalytic efficiency of l -nLDH toward pyruvate and the high transcription ratios of ldhL to ldhD and ldhL to the GOX gene provide the key explanations for the high optical purity of l -lactic acid produced by B. coagulans 2-6.

Plasmonic focusing with metallic probes has attracted extensive studies due to its successful applications in advanced technologies such as near-field scanning optical microscopy and tip-enhanced Raman spectroscopy. Here the fabrication and characterization of a unique spiral metallic taper with polarization-insensitive three-dimensional (3D) plasmonic focusing properties are reported. Metallic probes with spiral corrugations are readily fabricated along the surfaces of the conical structures with a 3D direct laser writing method followed by a metal deposition process. With the broken structural symmetry induced by the spiral corrugations, plasmonic focusing is demonstrated under excitation of linearly polarized light with different polarization directions. Moreover, apertures with various sizes can be flexibly introduced at the apex of the conical probe structures with direct fabrication, which enables the observation of scattered light from waveguide modes, cutoff of waveguide modes and scattering from surfaces plasmons, respectively. The studies provide a novel methodology of design, realization, and application of 3D plasmonic focusing structures.

The refractive index sensing capabilities of a 2D triangular-lattice photonic crystal (PhC) with defective and surface modes are studied. These are composed of silicon columns arranged in a liquid environment. Through changing the rods’ shape on the PhC’s surface from a circle to an ellipse and optimizing the sizes of two adjacent ellipses, the surface localized mode can be generated. Combining the central defective mode with surface modes, an ultra-small three-working-wavelength PhC refractive index sensor is proposed. The shift of the resonant wavelengths influenced by the slight alteration of the protein’s thickness attached by the special rods is studied, and it is found that a minimum alteration of the protein’s thickness of about 4 nm can be distinguished, and a maximum refractive index sensitivity of 0.516 is obtained. Three kinds of analytes can be detected in real-time and at the same time, which are bounded around the input/output surfaces and the central rods through biological specific binding.

Based on the nonlinear resonators and self-collimation characteristics of light beams, we designed an all-optical photonic crystal beam splitter and switch. The proposed device consists of an input waveguide and three output waveguides connected to different ring resonators. Three pump beams transmit through different resonators via the self-collimation effect, and eight output states are realized by altering the intensity of the pump light. The proposed device works at the wavelength of 1629.57 nm, and the pump wavelength is located at 1240.00 nm. The transmittance contrast between the "on" and "off" states reached a maximum value of 124.0 and a minimum of 17.6. The minimal pump light intensity required to implement the performance is only ${0.162}\,\,{\rm W/}\unicode{x00B5}{\rm m}^2$0.162W/µm2, while the maximal value is about ${0.497}\,\,{\rm W/}\unicode{x00B5}{\rm m}^2$0.497W/µm2. Due to the small size of our proposed device and also its insensitivity to the pump light beams' incident location and spatial width within a certain degree, it has great potential application value in all-optical communications.

Ultrasound fields have broad applications in imaging, sensing, medical therapy, etc. In these applications, it is of great importance to generate desired ultrasound fields. The generation of arbitrary ultrasound fields is challenging using phased array transducers or a monolithic acoustic hologram. In this work, by taking advantage of the photoacoustic effect and spatial light modulating technique, we demonstrate that dynamic and high-resolution arbitrary acoustic fields in liquid can be realized. We clearly show ultrasonic vortex and arbitrary 2D/3D ultrasonic fields in our photoacoustic system. All the measured pressure fields agree well with the desired ones. We anticipate these rapidly tunable photoacoustic fields will find applications in dynamic acoustic tweezers and ultrasonic imaging.

The sensitivities of the octagonal quasi-periodic photonic crystal (QPC) defective modes are theoretically studied. The octagonal QPC biosensors are composed of silicon columns arranged in a liquid background. By designing a defect structure, a variety of localized modes with different spatial symmetries and field profiles are obtained, and a maximum refractive index sensitivity 800 nm/RIU is achieved around 1500 nm transmission peak when the central rod's size equals 100 nm, and the corresponding detection limit reaches 0.00042. The liquid can flow freely among the rods through the entire structure, so it is convenient to monitor the concentration of protein in the liquid environment dynamically. The influence of the protein's thickness to the shift of the resonant wavelength is also studied, where a minimum protein's thickness of less than 10 nm can be detected by optimizing the central column's size to be 400 nm, and the spatial field profiles of different resonant modes are analyzed to explain the corresponding sensitivities.

Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

Here we propose a scheme utilizing the double plasmon modes of gold nanorod (GNR) to efficiently enhance the fluorescence of surrounding emitters. The transversal and longitudinal surface plasmon resonance (TSPR and LSPR, respectively) modes of GNR are simultaneously utilized to enhance the excitation and emission efficiency, respectively. To demonstrate the idea, GNRs coated with an Oxazine-725 dye molecule-doped silica shell are employed. For comparison, gold nanospheres with the same shell are also studied, of which the single plasmon resonance mode matches only with the excitation wavelength of Oxazine-725. The experimental results, in agreement with theoretical simulations using the discrete dipole approximation method, successfully demonstrate the efficient excitation and emission enhancement of fluorescence assisted by the double SPRs of GNRs.

Optical tweezers have become an efficient tool to trap microscopic and nanoscopic objects and manipulate their mechanical motion via optical forces and torques [1–3]. In this talk we discuss our recent experimental and theoretical works on trapping and manipulation of micrometer-size Janus particle with half surface of polystyrene particle coated with nanometer-thick gold thin film in various optical tweezers, such as point, circular, and linear traps [4, 5]. As the Janus particle is asymmetric in geometry and physical properties, the focused laser beam, either in point, circular, or linear shape spot, not only exert an optical force that will push forward the particle along a revolution orbit surrounding the optical axis of the laser beam, but also an optical torque that will cause rotation of the particle around its own axis. The simultaneous revolution and rotation of the Janus particle can be controlled via several parameters, such as the power and the size of the optical tweezers. To fully understand the physics underlying the experimental observation of the complicated mechanical motions, we develop a ray-optics model to calculate the optical force and torque of Janus particle in point, circular, and linear traps. The calculation results quantitatively agree with experimental data. These studies will help to develop new optical tweezers to enable better control of the mechanical motion of various microscopic and nanoscopic particles of complicated geometric and physical configurations.

The self-assembly behavior of the mixture of tetra-tert-butyl zinc(II) phthalocyanine (TB-ZnPc) isomers on a Au(111) surface has been investigated by means of scanning tunneling microscopy (STM). Four tert-butyl groups are added to four peripheral benzene rings of zinc(II) phthalocyanine, which gives the planar molecules a three-dimensional structure. Two possible substituting locations for each tert-butyl group result in a mixture of structural isomers, which are easily identified by STM. Two different structures have been distinguished in the monolayer regime depending on the preparation procedure. One is a quasi-ordered structure whereby the molecules are arranged in the closest-packed way, and the second is an ordered structure in which the molecules are arranged side by side. The more ordered molecular network in the latter is considered to be a consequence of unification of TB-ZnPc isomers.

The unbinding force of microtubule-AtMAP65-1 bond is measured with dual-optical tweezers. Force histograms reveal quantized force distributions under physiological condition and with 100 mM NaCl treatment. Based on Bell-Evans-model of multiple bonds, histograms are fitted and kinetic parameters are obtained. Under the force loading rate of 9pN/s, the most probable unbinding forces for the single bond are 16.8 +/- 0.8 and 14.7 +/- 0.8 pN under the physiological and treatment conditions, respectively. Position of transition state of the bond is given to be Delta x = 2.1 +/- 0.1 nm both with and without treatment of NaCl. Intrinsic dissociation rate constants k(0) are 0.0010 +/- 0.0002 and 0.0020 +/- 0.0005 s(-1) corresponding to without and with NaCl treatment, which means that 100 mM NaCl shortens the natural lifetime of the bond by 50%. In addition, the activation barrier also changes by 3.4% after treatment with NaCl, which indicates that NaCl makes the dissociation of the bond easier.

Bistable rotation is realized for a gold-coated Janus colloidal particle in an infrared optical trap. The metal coating on the Janus particles are patterned by sputtering gold on a monolayer of closely packed polystyrene particles. The Janus particle is observed to stably rotate in an optical trap. Both the direction and the rate of rotation can be experimentally controlled. Numerical calculations reveal that the bistable rotation is the result of spontaneous symmetry breaking induced by the uneven curvature of the coating patterns on the Janus sphere. Our results thus provide a simple method to construct large quantities of fully functional rotary motors for nano- or microdevices.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of high precision and damage-free analysis of living biological objects.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of highprecision and damage-free analysis of living biological objects.

We report on Ge nanocluster formation on Si(1 1 1)-7 × 7 surface at elevated substrate temperatures during deposition. The shape and size of the Ge clusters are more uniform than those obtained at room temperature due to an increase in the average mobility of the additional atoms. The Ge clusters have a preferential adsorption site in the faulted halves. Some clusters in the faulted and the unfaulted halves exhibit two different features, which indicate the different adsorption energy and chemical activity of the two half-cells. We also observe some clusters forming in a characteristic star shape at a particular positive bias voltage. The formation mechanism and possible structures are discussed.

A novel class of moire fringe patterns in scanning tunnelling microscope (STM) imaging is presented and analysed in this paper. The moire fringe is generated from the interference of the atomic lattice of the specimen and STM scanning lines. Both parallel and rotational STM moire fringes of the surface of highly oriented pyrolytic graphite (HOPG) are investigated. The formation principle and experimental techniques of STM moire fringes are discussed. Nanometre scale resolution and sensitivity are found in the moire fringe patterns. They precisely magnify the STM image of lattice irregularities. A potential application—measuring surface deformation and defects in the nanometre range—is proposed.