Study on the combination of virtual machine tools and wearable vibration devices for operators experiencing cutting forces in the milling process.

The primary goal of this study is to develop a wearable system for providing CNC machine operators with visual and tactile perception of triaxial cutting forces, thereby assisting operators in industrial environments to enhance work efficiency and prevent mechanical failures. To achieve this goal, we successfully integrated a virtual machining tool simulator with the remote-control wearable system (RCWS). Using the 'King Path' milling parameters, we employed the simulation software developed by the AIM-HI team to calculate static and dynamic cutting forces, converting this data into vibrational commands for the RCWS to generate corresponding tactile feedback. Furthermore, we conducted extensive experiments, testing various data conversion methods, including three sampling techniques and two data compression strategies, aiming to provide accurate tactile feedback related to cutting forces under different operating conditions.

Association between aspirin use and risk of dementia: a systematic review and meta-analysis.

PURPOSE: Dementia and Alzheimer's disease (AD) pose significant challenges to public health globally with no effective treatment strategies available. Therefore, the research focuses on developing effective prophylaxis to prevent the onset of these diseases. Recent studies have suggested that low-dose aspirin may help reduce the risk of dementia. Nonetheless, evidence regarding the correlation between aspirin consumption and the onset of dementia and AD is limited. This review aims to provide an up-to-date summary of the existing evidence and evaluate the association between aspirin and the onset of dementia and Alzheimer's disease. METHODS: A systematic search of PubMed, Embase, Web of Science, PsycINFO, and CINAHL databases was conducted to find eligible studies published until April 2023. A random-effects meta-analysis of the eligible studies was then performed to assess the link between aspirin use and the onset of dementia and Alzheimer's disease. Additionally, we conducted subgroup analyses to evaluate the overall effect of low-dose (75-100 mg) aspirin consumption on the onset of dementia and AD. RESULTS: A total of 875 studies were identified, with only 22 meeting the inclusion criteria. There was no statistically significant impact of aspirin consumption on the onset of dementia (HR 1.13, 11 studies) or Alzheimer's disease (HR 0.91, 3 studies). Additionally, subgroup analysis showed that taking low doses of aspirin (75-100 mg) did not significantly affect the onset of either dementia (HR 0.96, 13 studies) or Alzheimer's disease (HR 0.85, 2 studies). CONCLUSIONS: Aspirin use does not decrease the risk of dementia or AD, even when taken in low doses. However, the quality of the studies analyzed was inadequate, with only three randomized controlled trials included in the review. Future high-quality studies are needed to assess the effect of aspirin consumption on these diseases. These findings may assist clinicians in selecting appropriate prophylactic strategies for patients at risk of developing dementia and AD.

Piezoelectric Micromachined Ultrasonic Transducer-Integrated Helmholtz Resonator with Microliter-Sized Volume-Tunable Cavity.

In this study, a piezoelectric micromachined ultrasonic transducer (PMUT) is integrated with a microliter-sized volume-tunable Helmholtz resonator. The passive Helmholtz resonator is constructed using an SU8 photolithography-defined square opening plate as the neck portion, a 3D-printed hollow structure with a threaded insert nut, and a precision set screw to form the volume-controllable cavity of the Helmholtz resonator. The fabricated piezoelectric films acted as ultrasonic actuators attached to the surface of the neck SU8 plate. Experimental results show that the sound pressure level (SPL) and operation bandwidth could be effectively tuned, and a 200% SPL increase and twofold bandwidth enhancement are achieved when setting the cavity length to 0.75 mm compared with the open-cavity case. A modified Helmholtz resonator model is proposed to explain the experimental results. The adjusting factors of the effective mass and viscous damper are created to modify the existing parameters in the conventional Helmholtz resonator model. The relationship between the adjusting factors and cavity length can be described well using a two-term power series curve. This modified Helmholtz resonator model not only provides insight into this active-type Helmholtz resonator operation but also provides a useful estimation for its optimal design and fabrication.

The simplified hybrid model based on BP to predict the reference crop evapotranspiration in Southwest China.

The accurate prediction of reference crop evapotranspiration is of great significance to climate research and regional agricultural water management. In order to realize the high-precision prediction of ETO in the absence of meteorological data, this study use XGBoost to select key influencing factors and BP algorithm to construct ETO prediction model of 12 meteorological stations in South West China in this study. ACO, CSO and CS algorithms are used to optimize the model and improve the adaptability of the model. The results show that Tmax, n and Ra can be used as the input combination of ETO model construction, and Tmax is the primary factor affecting ETO. ETO model constructed by BP algorithm has good goodness of fit with the ETO calculated by FAO-56 PM and ACO, CSO and CS have significant optimization effect on BP algorithm, among which CSO algorithm has the best optimization ability on BP, with RMSE, R2, MAE, NSE, GPI ranging 0.200-0.377, 0.932-0.984, 0.140-0.261, 0.920-0.984, 1.472-2.000, GPI ranking is 1-23. Therefore, the input combination (Tmax, n and Ra) and CSO-BP model are recommended as a simplified model for ETO prediction in Southwest China.

Electroactive polymer-based inner vessel-wall pressure transducer capable of integration with a PTA balloon catheter for examining blood vessel health.

This study presents a state-of-the-art soft and biocompatible transducer capable of detecting vessel inner-wall pressure for biomedical applications. The device includes a 3D electroactive polymer core element encapsulated by polydimethylsiloxane with an ellipsoidal structure. The device produces a voltage output when its sensing mechanism experiences different pressures, resulting in deformation at different orientations. Thus, it can be employed to detect the pressure exerted by inner vessel walls of different stiffness values. The output voltage is induced by the strain experienced by the sensing mechanism of the device without the need for any external electrical power source. The core element, which is made of an ionic polymer-metal composite, possesses a unique hollow design; this allows a catheter to pass through, and the core element can be anchored at an arbitrary position on the catheter. We also demonstrate that the fabricated device can be integrated with a medically used percutaneous transluminal angioplasty balloon catheter to form a smart sensing module. This module can detect different levels of fat accumulation around the inner wall of a blood vessel phantom. Evaluating vessel blockage and stiffness using the signals acquired from the developed device is discussed.

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding.

This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method.

An Out-of-Plane Operated Soft Engine Driving Stretchable Zone Plate for Adjusting Focal Point of an Ultrasonic Beam.

This paper presents a soft engine which performs up-and-down motion with four planar film-structured ionic polymer-metal composites (IPMC) actuators. This soft engine assembled with a stretchable Fresnel zone plate is capable of tuning the focus of ultrasonic beam. Instead of conventional clamps, we employ 3D printed frame pairs with magnets and a conductive gold cloth to provide an alternative solution for securing the IPMC actuators during assembly. The design and analysis of the zone plate are carefully performed. The zone plate allows the plane ultrasonic wave to be effectively focused. The motion of IPMC actuators stretch the metal-foil-made zone plate to tune the focal range of the ultrasonic beam. The zone plate, 3D frames and IPMC actuators were fabricated, assembled and tested. The stiffness normal to the stretchable zone plate with varied designs was investigated and the seven-zone design was selected for our experimental study. The force responsible for clamping the IPMC actuators, controlled by the magnetic attraction between the fabricated frames, was also examined. The driving voltage, current and resulting displacement of IPMC actuation were characterized. The developed soft engine stretching the zone plate to tune the focal point of the ultrasonic beam up to 10% was successfully demonstrated.

Neuroendocrine abnormalities associated with untreated first episode patients with major depressive disorder and bipolar disorder.

There are few studies that explore simultaneously the relationship of neuroendocrine hormones of the HPA, HPT and HPG axes with major depressive disorder (MDD) and bipolar disorder (BD). The aim of this study is to examine the relationship of neuroendocrine pathways with affective disorders by comparing the differences in measures of neuroendocrine function between untreated first episode patients with MDD and BD. A cohort of 679 MDD and 83 BD patients was recruited. Thyroid stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (FT3), thyroxine (T4), free thyroxin (FT4), cortisol (COR), adrenocorticotropic hormone (ACTH), estradiol (E2) and testosterone (T) were determined by chemiluminesent immunoassay for all patients. COR and ACTH were both significantly higher in the MDD group than those in BD group. The incidences of high secretion of ACTH and COR, and low thyroid hormone secretion were significantly greater in MDD patients than in BD patients. Decreased T secretion was more common in BD than MDD patients. ACTH was significantly positively correlated with HAMD total score and negatively correlated with FT3 in MDD patients. FT3 and FT4 levels were significantly negatively correlated with the somatoform factor score of HAMD in MDD patients. Untreated first episode patients with MDD have a hyperactivity of the HPA axis, lower HPT compared with BD patients. BD patients had reduced testosterone secretion. These findings indicate that ACTH, FT3 and FT4 could be used as markers for severity and symptoms of untreated first episode patients with MDD.

Classification between digs and dust particles on optical surfaces with acquisition and analysis of polarization characteristics.

In the automatic detection for surface defects of optical components, the digs and dust particles exhibit similar features: point-like shape and variable intensity reflectivity. On this condition, these two types with entirely different damages are easily confused so that misjudgments will be induced. To solve this problem, a polarization-characteristics-based classification method of digs and dust particles (PCCDD) is proposed based on the polarimetric imaging technique and dark-field imaging technique. First, a dark-field imaging system equipped with a polarization state generator (PSG) and a polarization state analyzer (PSA) is employed to measure and establish normalized Mueller matrices' datasets of digs and dust particles. And by a nonlinear global search combined with a separability evaluation method, the optimal number of acquisitions and corresponding polarization measurement states of the PSG and the PSA are obtained, as well as the parameters of classification function. Then, multiple polarization images are acquired under the optimal states to extract a multidimensional feature description that relates only to the polarization characteristics of the defect; this subsequently acts as the input vector of the classifier to finally achieve the classification. This method takes full advantage of both the difference in polarization properties between digs and dust particles and the characteristic that the polarization properties of digs are relatively invariant while those of dust particles have a large variability. The classification process involves only simple matrix operations. Compared to the traditional discrimination method based on intensity images, the features obtained by this method have a higher separability. Experiments show that the classification accuracy reaches over 90%. This method can be further applied to the recognition and discrimination of other defects in the field of surface defects' detection.

Overview of the improvement of the ring-stage survival assay-a novel phenotypic assay for the detection of artemisinin-resistant Plasmodium falciparum.

Artemisinin resistance in Plasmodium falciparum threatens the remarkable efficacy of artemisinin-based combination therapies worldwide. Thus, greater insight into the resistance mechanism using monitoring tools is essential. The ring-stage survival assay is used for phenotyping artemisinin-resistance or decreased artemisinin sensitivity. Here, we review the progress of this measurement assay and explore its limitations and potential applications.

Hydrothermally synthesized PZT film grown in highly concentrated KOH solution with large electromechanical coupling coefficient for resonator.

This paper presents a study of lead zirconate titanate (PZT) films hydrothermally grown on a dome-shaped titanium diaphragm. Few articles in the literature address the implementation of hydrothermal PZT films on curved-diaphragm substrates for resonators. In this study, a 50-µm-thick titanium sheet is embossed using balls of designed dimensions to shape a dome-shaped cavity array. Through single-process hydrothermal synthesis, PZT films are grown on both sides of the processed titanium diaphragm with good adhesion and uniformity. The hydrothermal synthesis process involves a high concentration of potassium hydroxide solution and excess amounts of lead acetate and zirconium oxychloride octahydrate. Varied deposition times and temperatures of PZT films are investigated. The grown films are characterized by X-ray diffraction and scanning electron microscopy. The 10-µm-thick PZT dome-shaped resonators with 60- and 20-µm-thick supporting layers are implemented and further tested. Results for both resonators indicate that large electromechanical coupling coefficients and a series resonance of 95 MHz from 14 MHz can be attained. The device is connected to a complementary metal-oxide-semiconductor integrated circuit for analysis of oscillator applications. The oscillator reaches a Q value of 6300 in air. The resonator exhibits a better sensing stability when loaded with water when compared with air.

Investigation on the Mechanical and Electrical Behavior of a Tuning Fork-Shaped Ionic Polymer Metal Composite Actuator with a Continuous Water Supply Mechanism.

This paper presents an innovative tuning fork-shaped ionic polymer metal composite (IPMC) actuator. With an integrated soft strain gauge and water supply mechanism (WSM), the surface strain of the actuator can be sensed in situ, and providing a continuous water supply maintains the water content inside the IPMC for long-term operation in air. The actuator was fabricated using a micromachining technique and plated with a nickel electrode. The device performance was experimentally characterized and compared with an actuator without a WSM. A large displacement of 1.5 mm was achieved for a 6 mm-long prong with 7-V dc actuation applied for 30 s. The measured current was analyzed using an electrochemical model. The results revealed that the faradaic current plays a crucial role during operation, particularly after 10 s. The measured strain confirms both the bending and axial strain generation during the open-and-close motion of the actuator prongs. Most of the water loss during device operation was due to evaporation rather than hydrolysis. The constructed WSM effectively maintained the water content inside the IPMC for long-term continuous operation.

Hypouricaemic action of mangiferin results from metabolite norathyriol via inhibiting xanthine oxidase activity.

Context Mangiferin has been reported to possess a potential hypouricaemic effect. However, the pharmacokinetic studies in rats showed that its oral bioavailability was only 1.2%, suggesting that mangiferin metabolites might exert the action. Objective The hypouricaemic effect and the xanthine oxidase inhibition of mangiferin and norathyriol, a mangiferin metabolite, were investigated. Inhibition of norathyriol analogues (compounds 3-9) toward xanthine oxidase was also evaluated. Materials and methods For a dose-dependent study, mangiferin (1.5-6.0 mg/kg) and norathyriol (0.92-3.7 mg/kg) were administered intragastrically to mice twice daily for five times. For a time-course study, mice received mangiferin and norathyriol both at a single dose of 7.1 µmol/kg. In vitro, inhibition of test compounds (2.4-2.4 mM) against xanthine oxidase activity was evaluated by the spectrophotometrical method. The inhibition type was identified from Lineweaver-Burk plots. Results Norathyriol (0.92, 1.85 and 3.7 mg/kg) dose dependently decreased the serum urate levels by 27.0, 33.6 and 37.4%, respectively. The action was more potent than that of mangiferin at the low dose, but was equivalent at the higher doses. Additionally, the hypouricaemic action of them exhibited a time dependence. In vitro, norathyriol markedly inhibited the xanthine oxidase activities, with the IC50 value of 44.6 µM, but mangiferin did not. The kinetic studies showed that norathyriol was an uncompetitive inhibitor by Lineweaver-Burk plots. The structure-activity relationships exhibited that three hydroxyl groups in norathyriol at the C-1, C-3 and C-6 positions were essential for maintaining xanthine oxidase inhibition. Discussion and conclusion Norathyriol was responsible for the hypouricaemic effect of mangiferin via inhibiting xanthine oxidase activity.

A more appropriate white blood cell count for estimating malaria parasite density in Plasmodium vivax patients in northeastern Myanmar.

The conventional method of estimating parasite densities employ an assumption of 8000 white blood cells (WBCs)/µl. However, due to leucopenia in malaria patients, this number appears to overestimate parasite densities. In this study, we assessed the accuracy of parasite density estimated using this assumed WBC count in eastern Myanmar, where Plasmodium vivax has become increasingly prevalent. From 256 patients with uncomplicated P. vivax malaria, we estimated parasite density and counted WBCs by using an automated blood cell counter. It was found that WBC counts were not significantly different between patients of different gender, axillary temperature, and body mass index levels, whereas they were significantly different between age groups of patients and the time points of measurement. The median parasite densities calculated with the actual WBC counts (1903/µl) and the assumed WBC count of 8000/µl (2570/µl) were significantly different. We demonstrated that using the assumed WBC count of 8000 cells/µl to estimate parasite densities of P. vivax malaria patients in this area would lead to an overestimation. For P. vivax patients aged five years and older, an assumed WBC count of 5500/µl best estimated parasite densities. This study provides more realistic assumed WBC counts for estimating parasite densities in P. vivax patients from low-endemicity areas of Southeast Asia.

Structure of Waxy Maize Starch Hydrolyzed by Maltogenic α-Amylase in Relation to Its Retrogradation.

Maltogenic α-amylase is widely used as an antistaling agent in bakery foods. The objective of this study was to determine the degree of hydrolysis (DH) and starch structure after maltogenic amylase treatments in relation to its retrogradation. Waxy maize starch was cooked and hydrolyzed to different degrees by a maltogenic amylase. High-performance anion-exchange chromatography and size exclusion chromatography were used to determine saccharides formed and the molecular weight (Mw) distributions of the residual starch structure, respectively. Chain length (CL) distributions of debranched starch samples were further related to amylopectin (AP) retrogradation. Differential scanning calorimetry (DSC) results showed the complete inhibition of retrogradation when starches were hydrolyzed to >20% DH. Mw and CL distributions of residual AP structure indicated that with an increase in %DH, a higher proportion of unit chains with degree of polymerization (DP) ≤9 and a lower proportion of unit chains with DP ≥17 were formed. A higher proportion of short outer AP chains that cannot participate in the formation of double helices supports the decrease in and eventual inhibition of retrogradation observed with the increase in %DH. These results suggest that the maltogenic amylase could play a powerful role in inhibiting the staling of baked products even at limited starch hydrolysis.

A self-strain feedback tuning-fork-shaped ionic polymer metal composite clamping actuator with soft matter elasticity-detecting capability for biomedical applications.

This paper presents a smart tuning-fork-shaped ionic polymer metal composite (IPMC) clamping actuator for biomedical applications. The two fingers of the actuator, which perform the clamping motion, can be electrically controlled through a unique electrode design on the IPMC material. The generated displacement or strain of the fingers can be sensed using an integrated soft strain-gage sensor. The IPMC actuator and associated soft strain gage were fabricated using a micromachining technique. A 13.5×4×2 mm(3) actuator was shaped from Nafion solution and a selectively grown metal electrode formed the active region. The strain gage consisted of patterned copper foil and polyethylene as a substrate. The relationship between the strain gage voltage output and the displacement at the front end of the actuator's fingers was characterized. The equivalent Young's modulus, 13.65 MPa, of the soft-strain-gage-integrated IPMC finger was analyzed. The produced clamping force exhibited a linear increasing rate of 1.07 mN/s, based on a dc driving voltage of 7 V. Using the developed actuator to clamp soft matter and simultaneously acquire its Young's modulus was achieved. This demonstrated the feasibility of the palpation function and the potential use of the actuator in minimally invasive surgery.

[CD160 characterization and its association with disease progression in patients with chronic HIV-1 infection].

OBJECTIVE: To explore the expression of CD160, a costimulator, on CD4(+) and CD8(+) T cells in chronic human immunodeficiency virus-1 (HIV-1) infected patients. METHODS: A total of 23 chronic HIV-1 infected patients were enrolled into 302 Hospital of People's Liberation Army from January 2010 to December 2011. Meanwhile, 20 healthy individuals were selected as healthy controls (HC). Peripheral blood was collected, peripheral blood mononuclear cells (PBMC) were isolated by density gradient centrifugation and CD160 was stained with fluorescent antibody. The expressions of CD160 on CD4(+) and CD8(+) T cell subsets were detected by flow cytometry and its correlation with CD4(+) T cell absolute number and HIV RNA viral load were analyzed. RESULTS: The expressions of CD160 on CD4(+) and CD8(+) T cell increased versus HC (on CD4(+) T cells, percentage: (14.3 ± 7.5)% vs (3.9 ± 2.2)%, median fluorescent intensity (MFI): 26.4 ± 11.0 vs 12.4 ± 2.9; on CD8(+) T cells, percentage: (40.9 ± 13.2)% vs (12.9 ± 6.6)%, MFI: 52.5 ± 17.4 vs 18.2 ± 5.0). Furthermore, the expression of CD160 on CD4(+) T cells was negatively correlated with CD4(+) T cell absolute number (r = -0.550, P = 0.010) and positively with HIV RNA load (r = 0.522, P = 0.015). However, the expression of CD160 on CD8(+) T cells was not correlated with CD4(+) T cell absolute number or HIV RNA load. The expressions of CD160 on CD8(+) T cell subsets Tn, Tcm and Tem in patients with chronic HIV-1 infection increased compared with HC (25.3 ± 17.6 vs 5.0 ± 3.1, 45.8 ± 13.0 vs 20.4 ± 4.3, 37.0 ± 13.6 vs 20.0 ± 10.8). In addition, Tn subset decreased while Tcm subset increased in CD160(+) CD8(+) T cell subset distribution in patients with HIV-1 infection compared with HC subjects. CONCLUSION: CD160 may contribute to the exhaustion of CD4(+) and CD8(+) T cells and influence the distribution of memory CD8(+) T cell subsets.

Fabrication and characterization of a micromachined swirl-shaped ionic polymer metal composite actuator with electrodes exhibiting asymmetric resistance.

This paper presents a swirl-shaped microfeatured ionic polymer-metal composite (IPMC) actuator. A novel micromachining process was developed to fabricate an array of IPMC actuators on a glass substrate and to ensure that no shortcircuits occur between the electrodes of the actuator. We demonstrated a microfluidic scheme in which surface tension was used to construct swirl-shaped planar IPMC devices of microfeature size and investigated the flow velocity of Nafion solutions, which formed the backbone polymer of the actuator, within the microchannel. The unique fabrication process yielded top and bottom electrodes that exhibited asymmetric surface resistance. A tool for measuring surface resistance was developed and used to characterize the resistances of the electrodes for the fabricated IPMC device. The actuator, which featured asymmetric electrode resistance, caused a nonzero-bias current when the device was driven using a zero-bias square wave, and we propose a circuit model to describe this phenomenon. Moreover, we discovered and characterized a bending and rotating motion when the IPMC actuator was driven using a square wave. We observed a strain rate of 14.6% and a displacement of 700 µm in the direction perpendicular to the electrode surfaces during 4.5-V actuation.

Risk factors for liver-related mortality in chronic hepatitis C patients: a deceased case-living control study.

AIM: To investigate the risk factors for liver-related mortality in chronic hepatitis C (CHC) patients. METHODS: All deceased CHC inpatient data were collected from the Beijing 302 Hospital clinical database, which includes more than 8250 CHC inpatients during the period from 2002 to 2012. The controls were matched to cases by age (± 2 years), sex and date of hospital admission (within the same year). Potential risk factors were included for the evaluation, and odds ratios (OR) and 95%CI were estimated using univariate (unadjusted) and multivariate (adjusted OR, AOR) conditional logistic regression. All statistical tests were two-sided. P values < 0.05 were considered statistically significant. RESULTS: Based on examinations of 144 CHC-related deceased cases and 576 controls, we found that antiviral therapy with interferon-α was associated with a 47% decrease in the risk of hepatic mortality (AOR = 0.53, 95%CI: 0.28-0.99, P = 0.048). Additionally, the initial diagnostic stage of the disease (AOR = 2.89, 95%CI: 1.83-4.56 and P < 0.001 for liver cirrhosis/AOR = 8.82, 95%CI: 3.99-19.53 and P < 0.001 for HCC compared with CHC), diabetes (AOR = 2.35, 95%CI: 1.40-3.95, P = 0.001), hypertension (AOR = 1.76, 95%CI: 1.09-2.82, P = 0.020), alcohol consumption (AOR = 1.73, 95%CI: 1.03-2.81, P = 0.037) and HBsAg positivity (AOR = 22.28, 95%CI: 5.58-89.07, P < 0.001) were associated with a significant increase in the risk of liver-related mortality in CHC patients. CONCLUSION: This study indicates that interferon-α treatment, the stage at the initial diagnosis of the disease and comorbidities are all independent risk factors for liver-related mortality in CHC patients.

Refrigeration provides a simple means to synchronize in vitro cultures of Plasmodium falciparum.

Plasmodium falciparum is usually asynchronous during in vitro culture. Highly synchronized cultures of P. falciparum are routinely used in malaria research. Here, we describe a simple synchronization procedure for P. falciparum asexual erythrocytic culture, which involves storage at 4°C for 8-24 h followed by routine culture. When cultures with 27-60% of ring stage were synchronized using this procedure, 70-93% ring stages were obtained after 48 h of culture and relative growth synchrony remained for at least two erythrocytic cycles. To test the suitability of this procedure for subsequent work, drug sensitivity assays were performed using four laboratory strains and four freshly adapted clinical P. falciparum isolates. Parasites synchronized by sorbitol treatment or refrigeration showed similar dose-response curves and comparable IC50 values to four antimalarial drugs. The refrigeration synchronization method is simple, inexpensive, time-saving, and should be especially useful when large numbers of P. falciparum culture are handled.