Atomic resolution imaging using a novel, compact and stiff scanning tunnelling microscope in cryogen-free superconducting magnet.

We present the design and performance of a novel scanning tunnelling microscope (STM) operating in a cryogen-free superconducting magnet. Our home-built STM head is compact (51.5 mm long and 20 mm in diameter) and has a single arm that provides complete openness in the scanning area between the tip and sample. The STM head consists of two piezoelectric tubes (PTs), a piezoelectric scanning tube (PST) mounted on a well-polished zirconia shaft, and a large PT housed in a sapphire tube called the motor tube. The main body of the STM head is made of tantalum. In this design, we fixed the sapphire tube to the frame with screws so that the tube's position can be changed quickly. To analyse the stiffness of the STM head unit, we identified the lowest eigenfrequencies with 3 and 4 kHz in the bending modes, 8 kHz in a torsional mode, and 9 kHz in a longitudinal mode by finite element analysis, and also measured the low drift rates in the X-Y plane and in the Z direction. The high performance of the home-built STM was demonstrated by images of the hexagonal graphite lattice at 300 K and in a sweeping magnetic field from 0 T to 9 T. Our results confirm the high stability, vibration resistance, insensitivity to high magnetic fields and the application potential of our newly developed STM for the investigation of low-frequency systems with high static support stiffness in physics, chemistry, material and biological sciences.

A rigid and compact piezoelectric motor with high output efficiency.

We introduce a novel piezoelectric stepper motor featuring high compactness, rigidity, and any direction operability. Here, not only is the structure of high novelty but also the working principle very simple. The piezo stacks unit is sandwiched between two spring finger pieces, with almost equal clamping forces applied between the top of the piezo stacks' unit and the spring finger piece. Applying individual driving signals to each of the five piezo stack pairs, causing deformation one by one in the same direction, followed by simultaneous recovery in the reverse direction, enables movement of the frame part. The optimized clamping force of the piezoelectric stack units and spring fingers ensures maximum output force. The motor's operational capability at low threshold voltages, specifically 8 V for downward movement and 10 V for upward movement, confirmed its efficacy in both vertical and horizontal directions. The motor's operational capability at a low threshold voltage of 10 V confirmed its efficacy in both vertical and horizontal directions. At room temperature, step size ranges from 0.3 to 7.4 µm at 20 Hz frequency and varying driving voltage from 10 to 180 V. It has a maximum travel range of about 5 mm and can lift a maximum load of 220 g in an upward direction, so the maximum output force generated by this motor is 2.2 N. The compact and rigid design is capable of building an atomically resolved scanning probe microscope, and its working ability has the potential to use the cleavage of different types of samples in limited space environments, such as the small-bore superconducting magnet and low temperature.

Glovebox-assisted magnetic force microscope for studying air-sensitive samples in a cryogen-free magnet.

Most known two-dimensional magnets exhibit a high sensitivity to air, making direct characterization of their domain textures technically challenging. Herein, we report on the construction and performance of a glovebox-assisted magnetic force microscope (MFM) operating in a cryogen-free magnet, realizing imaging of the intrinsic magnetic structure of water and oxygen-sensitive materials. It features a compact tubular probe for a 50 mm-diameter variable temperature insert installed in a 12 T cryogen-free magnet. A detachable sealing chamber can be electrically connected to the tail of the probe, and its pump port can be opened and closed by a vacuum manipulator located on the top of the probe. This sealing chamber enables sample loading and positioning in the glove box and MFM transfer to the magnet maintained in an inert gas atmosphere (in this case, argon and helium gas). The performance of the MFM is demonstrated by directly imaging the surface (using no buffer layer, such as h-BN) of very air-sensitive van der Waals magnetic material chromium triiodide (CrI3) samples at low temperatures as low as 5 K and high magnetic fields up to 11.9 T. The system's adaptability permits replacing the MFM unit with a scanning tunneling microscope unit, enabling high-resolution atomic imaging of air-sensitive surface samples.

A novel STM for quality atomic resolution with piezoelectric motor of high compactness and simplicity.

Scanning tunneling microscope (STM) is a renowned scientific tool for obtaining high-resolution atomic images of materials. Herein, we present an innovative design of the scanning unit with a compact yet powerful inertial piezoelectric motor inspired by the Spider Drive motor principle. The scanning unit mainly consists of a small 9 mm long piezoelectric tube scanner (PTS), one end of which is coaxially connected to the main sapphire body of the STM. Of particular emphasis in this design is the piezoelectric shaft (PS), constructed from piezoelectric material instead of conventional metallic or zirconium materials. The PS is a rectangular piezoelectric stack composed of two piezoelectric plates, which are elastically clamped on the inner wall of the PTS via a spring strip. The PTS and PS expand and contract independently with each other to improve the inertial force and reduce the threshold voltage. To ensure the stability of the PS and balance the stepping performance of the inertial motor, a counterweight, and a matching conical spring are fixed at the tail of the PS. This innovative design allows for the assessment of scanning unit performance by applying a driving signal, threshold voltage is 50 V at room temperature. Step sizes vary from 0.1 to 1 µm by changing the driving signal at room temperature. Furthermore, we successfully obtained atomic-resolution images of a highly oriented pyrolytic graphite (HOPG) sample and low drift rates of 23.4 pm/min and 34.6 pm/min in X-Y plane and Z direction, respectively, under ambient conditions. This small, compact STM unit has the potential for the development of a rotatable STM for use in cryogen-free magnets, and superconducting magnets.

Testing long-run relationship between agricultural gross domestic product and fruits production: evidence from Pakistan / Teste de relação de longo prazo entre o produto interno bruto agrícola e produçãode frutos: evidência do Paquistão

ABSTRACT: This paper analyses the long-run relationship between agricultural gross domestic product (GDP) and fruits production of Pakistan's economy over a period of 1961-2015 by employing Johansen and autoregressive distributed lag (ARDL) modern econometric technique. Three fruits were selected namely mango, apple and peach in this study. Augmented Dickey-Fuller and Phillips-Perron tests were used to check the data stationarity and conclude that the series are integrated of order one. The Johansen approach was applied to check the joint evolution of all the variables for co-integration. The Johansen test suggests that a long-run co-integration exists between agricultural GDP and fruits production. Results of the ARDL model (Bound test) detect the existence of long-run relationship between agricultural GDP and fruits production. The coefficient of the short-run form of ARDL model reveals that all the fruits have a positive impact on agricultural GDP. Moreover, the coefficients of the long-run form of ARDL model have apositive and significant influence on agricultural GDP of Pakistan. These results suggest that a 1% increase in mango, apple and peach production will increase agricultural GDP by 0.06%, 0.03% and 0.03% respectively. Finally, forecast error variance decomposition and impulse response function results depict that mango, apple and peach production significantly contributes to agricultural GDP in the case of Pakistan.

RESUMO: Este artigo analisa a relação de longa duração entre o Produto Interno Bruto agrícola (PIB) e a produção de frutos na economia do Paquistão durante um período de 1961-2015, empregando Johansen e o modelo ARDL (Autoregressive Distributed Lag) técnica de cointegração ou técnica de cointegração vinculada. Três frutas foram selecionadas neste estudo: manga, maçã e pêssego. Testes aumentados de Dickey-Fuller e Phillips-Perron foram utilizados para verificar a estacionária de dados e concluir que a série está integrada na ordem um. A abordagem de Johansen foi aplicada para verificar a evolução conjunta de todas as variáveis para a cointegração. O teste de Johansen sugere que existe uma cooperação de longa duração entre o PIB agrícola e a produção de frutos. Os resultados do modelo ARDL (Bound test) detectam a existência de uma relação de longa duração entre o PIB agrícola e a produção de frutos. O coeficiente da forma de curto prazo do modelo ARDL revela que todos os frutos têm um impacto positivo no PIB agrícola. Além disso, os coeficientes da forma de longo prazo do modelo ARDL têm uma influência positiva e significativa sobre o PIB agrícola do Paquistão. Estes resultados sugerem que um aumento de 1% na produção de manga, maçã e pêssego irá aumentar o PIB agrícola em 0,6%, 0,3% e 0,3%, respectivamente. Finalmente, a previsão de desvio de erros e resultados da função de resposta de impulso retratam que a produção de manga, maçã e pêssego contribui significativamente para o PIB agrícola do Paquistão.

Factors influencing the adoption of improved cultivars: a case of peach farmers in Pakistan / Fatores que influenciam a adoção de cultivares melhoradas: um caso de produtores de pêssego no Paquistão

ABSTRACT: This study aimed to investigate factors influencing the adoption of improved cultivars (ICs) in peach production in Khyber Pakhtunkhwa province of Pakistan. A total of 270 respondents were randomly selected from the three different cultivated areas of Khyber Pakhtunkhwa, namely, Peshawar, Nowshera and Swat. Binary choice model was used in this study to categorise the ICs of peach farmers into adoption and non-adoption. The study identifies that socio-economic, institutional farm resources, and climatic factors are influencing the adoption of ICs of peach production. Results of the estimated model reveal that farmer's age, education, household size, membership, cell phone, farm size, extension services and the role of the non-government organization have a positive effect on adoption of ICs. In addition, farmer's experience, off-farm income, livestock and machinery ownership, credit access and inputs prices have a positive and significant impact on ICs adoption. Moreover, results of the logit model demonstrate that climatic related factors have a highly significant and positive impact on the adoption of ICs. These results suggested that institutional services should be strengthened to provide managerial and technical skills on ICs technology adoption and on time provision of financial services to enhance the productivity of peach farmers.

RESUMO: Este estudo tem como objetivo investigar os fatores que influenciam a adoção de cultivares melhoradas (ICs) na produção de pessegueiros na província de Khyber Pakhtunkhwa, no Paquistão. Um total de 270 entrevistados foram selecionados aleatoriamente a partir das três diferentes áreas cultivadas de Khyber Pakhtunkhwa, Peshawar, Nowshera e Swat. O modelo de escolha binária foi usado neste estudo para categorizar os ICs dos produtores de pêssego em adoção e não-adoção. O estudo identifica que fatores socioeconômicos, institucionais, recursos agrícolas e climáticos influenciam a adoção de ICs de produção de pêssego. Os resultados do modelo estimado revelam que a idade do agricultor, educação, tamanho do agregado familiar, adesão, telefone celular, tamanho da fazenda, serviços de extensão e o papel da organização não-governamental têm efeito positivo sobre a adoção de ICs. Além disso, a experiência do agricultor, a renda fora da propriedade, a posse de gado e maquinaria, acesso ao crédito e preços dos insumos têm um impacto positivo e significativo na adoção dos ICs. Os resultados do modelo logit demonstram que os fatores climáticos relacionados têm um impacto altamente significativo e positivo na adoção de ICs. Estes resultados sugerem que os serviços institucionais devem ser fortalecidos para prover habilidades gerenciais e técnicas na adoção de tecnologia de ICs e no fornecimento de serviços financeiros para aumentar a produtividade dos produtores de pêssego.