Temporary Charge Research Articles

Hierarchical Equations of Motion for Quantum Chemical Dynamics: Recent Methodology Developments and Applications.

ConspectusQuantum effects are critical to understanding many chemical dynamical processes in condensed phases, where interactions between molecules and their environment are usually strong and non-Markovian. In this Account, we review recent progress from our group in development and application of the hierarchical equations of motion (HEOM) method, highlighting its ability to address some challenging problems in quantum chemical dynamics.In the HEOM method, the bath degrees of freedom are represented using effective modes from exponential decomposition of the bath correlation function. Complex spectral densities and low temperature simulations often require a larger number of modes, making the simulations very expensive. Recent advances, such as the barycentric spectral decomposition (BSD) technique, can significantly reduce the number of effective modes, allowing to handle complex spectral densities and enabling simulations at very low temperatures, including near-zero temperature dynamics.Another key improvement in the computational efficiency is the use of tensor network methods like matrix product states and hierarchical tensor networks. These techniques allow for efficient HEOM propagation with thousands of effective modes, crucial for simulating large molecular systems interacting with multiple baths. This combination enables simulations of excitation energy transfer (EET) in systems like the Fenna-Matthews-Olson (FMO) complex and even larger systems with experimentally determined spectral densities.The versatility of the HEOM method is demonstrated through applications to a wide range of chemical dynamics problems. Simulations of EET and related ultrafast spectroscopy are first briefly covered. Applications of the HEOM to quantum tunneling effects in proton transfer reactions are then presented. Early works have studied the non-Kramers dependence of the rate constant as a function of bath friction due to deep tunneling and revealed vibrationally nonadiabatic dynamics within the so-called nontraditional view of proton transfer reactions. A recent work on the large kinetic isotope effects in soybean lipoxygenase also indicated that many quantum correction approximations to classical transition-state theory may fall short in describing deep tunneling effects.Charge transport and separation dynamics in organic semiconductors are another area where the HEOM method has been instrumental. We first demonstrate that the HEOM provides a unified description of both band-like and thermally assisted charge carrier transport in organic materials. The effect of non-nearest neighbor transitions is then investigated by combining generalized master equations with exact memory kernels. The HEOM method also enables simulation of charge separation in organic photovoltaics (OPVs) and reveals how factors such as external electric fields, entropy, and charge delocalization influence the charge separation barrier and dynamics.Moreover, HEOM has been applied to investigate hydrogen atom scattering on the Au(111) surface and vibrational energy relaxation at molecule-metal interfaces. These studies provide deeper insights into how electron-hole pair excitations and temporary charge transfer states influence the nuclear motion, offering a new framework for simulating nonadiabatic dynamics on metal surfaces.In summary, the HEOM method has developed into a robust tool for simulating quantum effects in condensed phases. Future developments in algorithm efficiency and computational power will likely expand its applicability to even more complex systems.

Temperature-dependent electrowetting behavior on Teflon AF1600

In the growing application field of electrowetting (EW), reliable control of the wetting behavior by an applied voltage is required over a wide temperature range. Despite the rising interest of EW, only few data are reported in the literature on the EW behavior as a function of temperature. In this paper, we investigate the quasi-static EW response on one of the most widely used hydrophobic materials, Teflon AF1600, in a temperature range from 25 to 70,^{circ }mathrm{C}. The contact angle versus voltage is analyzed to illustrate the EW behavior. The results are in good agreement with the friction-adsorption model, which explains the contact angle (CA) hysteresis by a temperature-independent friction-like force and a temperature-dependent contribution of liquid adsorption onto a dielectric surface. The EW-CAs show a small asymmetry with respect to the polarity of the applied voltage, which might be due to the temporary and reversible charge trapping on the dielectric layer. The results underline that the different effects of the temperature-independent friction force and the temperature-dependent adsorption need to be taken into account to predict and control the CA in any EW-based application scenario.Graphical abstract

Detection of Proton Carriers in Tyrosine-Rich Peptide Thin Film

Traditional Von Neumann structure, where memory and computational units are separated, is now facing significant difficulties in terms of power consumption and computing speed in big data era. Therefore, human brain-like computing architecture is now paid attention in research field owing to its high parallelism, fault tolerance and robustness1-2. In this biological system, synaptic weight which plays crucial role in memory and learning is modulated by ionic species, especially protons transmitted between synapses. Here, we focused on short length peptide Y7C (YYACAYY) thin film which induces proton coupled electron transfer (PCET) due to its Tyrosine-rich structure. The Y7C film has shown an interesting behavior in which electrical conductivity varies with humidity3-4. By this modulation, bimodal memristor using both of voltage and humidity5 input and synaptic transistor which shows dynamic reponses through humidity have been demonstrated, but direct relation between current and proton conduction is still ambiguous. Therefore, we measured transient current flow between Pd and Au electrode and detected proton conduction of Y7C film.In previous studies, voltage & humidity controlled Y7C bimodal memristor has been reported. However, since the current regulation through humidity showed insufficient response than that through voltage, a definite relationship between moisture and current needs to be defined. To achieve that, thin film of the peptide material dissolved in Trifluoroacetic acid (TFA) 99% solution was spin coated on SiO2/Si substrate. By measuring the transient current of the Y7C film, presence of temporary charge carriers was observed. Also, the electrical impedance spectroscopy (EIS) of peptide layer showed a semicircle and a nonvertical tail, which indicate ionic conduction through the film. Lastly, film characterization of Y7C thin layer unveiled that the corresponding ions are protons as originally targeted. This research has showed principles of peptide thin film’s current increment driven by both of humidity and voltage through electrochemical reaction. Fig.1. Transient charge flowing through Y7C thin film measured in various atmospheric conditions and electrodes Acknowledgment This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1A2C2004864). References Pakkenberg B, Pelvig D, Marner L, Bundgaard M J, Gundersen H J G, Nyengaard J R and Regeur L 2003 Exp. Gerontol. 38 95Abbott L F and Nelson S B 2000 Nat. Neurosci. 3 1178Lee, Jaehun, et al. "Proton conduction in a tyrosine‐rich peptide/manganese oxide hybrid nanofilm." Advanced Functional Materials 27.35 (2017): 1702185.Sung, Taehoon, et al. "Effects of proton conduction on dielectric properties of peptides." RSC advances 8.59 (2018): 34047-34055.Song, Min-Kyu, et al. "Proton-enabled activation of peptide materials for biological bimodal memory." Nature Communications 11.1 (2020): 1-8. Figure 1

The Role of Areca catechu Extract on Decreasing Viscosity of Vegetable Oils.

The direct use of vegetable oil is constrained by vegetable oils' viscosity, which is relatively high. Therefore, this study discusses reducing the vegetable oils viscosity molecularly, using natural additives of Areca extract. The role of Areca extract on diminishing the viscosity of vegetable oil was simulated utilizing HyperChem software. Then, the viscosity was verified using the ASTM D445 method. The results show that the epicatechin in the Areca extract generates a local magnetic field on its aromatic ring that plays the role of energizing electron mobility in vegetable oil. On the one hand, increased electron mobility decreases oil polarity but, on the other hand, increases the London force via a temporary dipole charge. Simultaneously, it relaxes oil molecules that tend to increase molecule distance decreasing the London force. Since viscosity is proportional to the London force and oil polarity; thus, these three phenomena determine the role of Areca extract on the oil viscosity. The viscosity reduction is smaller at a larger number of the double bonds in the fatty acid chain since the local magnetic field's induction on the electron spin is interrupted in the double bonds

Concept of climate-charged airspaces: a potential policy instrument for internalizing aviation's climate impact of non-CO2 effects

ABSTRACT Approximately 50–75% of aviation's climate impact is caused by non-CO2 effects, like the production of ozone and the formation of contrail cirrus clouds, which can be effectively prevented by re-routing flights around highly climate-sensitive areas. Here, we discuss options how to incentivize re-routing approaches and apply multicriteria trajectory optimizations to demonstrate the feasibility of the concept of climate-charged airspaces (CCAs). We show that although climate-optimized re-routing results in slightly longer flight times, increased fuel consumption and higher operating costs, it is more climate-friendly compared to a cost-optimized routing. In accordance to other studies, we find that the averaged temperature response over 100 years (ATR) of a single flight can be reduced by up to 40%. However, if mitigation efforts are associated with a direct increase in costs, there is a need for climate policies. To address the lack of incentivizing airlines to internalize their climate costs, this study focuses on the CCA concept, which imposes a climate charge on airlines when operating in highly climate-sensitive areas. If CCAs are (partly) bypassed, both climate impact and operating costs of a flight can be reduced: a more climate-friendly routing becomes economically attractive. For an exemplary North-Atlantic network, CCAs create a financial incentive for climate mitigation, achieving on average more than 90% of the climate impact reduction potential of climate-optimized trajectories (theoretical maximum, benchmark). Key policy insights Existing climate policies for aviation do not address non- effects, which are very sensitive to the location and the timing of the emission. By imposing a temporary climate charge for airlines that operate in highly climate-sensitive regions, the trade-off between economic viability and environmental compatibility could be resolved: Climate impact mitigation of non- effects coincides with cutting costs. To ensure easy planning and verification, climate charges are calculated analogously to en-route and terminal charges. For climate mitigation it is therefore neither necessary to monitor emissions ( , etc.) nor to integrate complex non- effects into flight planning procedures of airlines. Its implementation is feasible and effective.

Evolution of calcite surfaces upon thermal decomposition, characterized by electrokinetics, in-situ XRD, and SEM

The present study analyses transformation pathways of pristine and thermally treated porous limestone and dense marble surfaces by means of time-resolved streaming current and potential measurements coupled with scanning electron microscopy and in-situ X-ray diffraction. The results reveal that under nonequilibrium conditions the zeta potential (ζ) of natural carbonates may exhibit positive and negative signs and ζ drifts in opposite directions. Sample surface roughness influences ζ because it contributes to dissolution, as observed particularly in the initial period of time-resolved measurements. Thermal treatment causes a temporary charge reversal from negative to positive. The reactivity of calcium hydroxide on calcite surfaces governs the net electrokinetic potential and isoelectric point (IEPpH), even at low surface coverage, as cross-validated by in-situ XRD. It was also found that pore conductivity may lead to ~90% underestimation of ζ when assessed by streaming potential. SEM studies revealed micro cracks inducement on marble after thermal treatment, which can result in underestimation of ζ up to the same extent as for the porous limestone. When an asymmetric cell configuration involving calcite and polypropylene surfaces is used, the fractional contribution of polypropylene to the IEPpH is 0.3 and to the overall determined ζ up to 0.5. Our findings contribute to the understanding of nonequilibrium and time-dependent electrokinetic potential modifications associated with the reactivity of porous surfaces. This study highlights the effectiveness of the streaming potential technique for monitoring such changes further supported by the use of ancillary techniques to analyze the extend of chemo-mineralogical and physical alterations.

Assessment of the starter motor system use powered by capacitive power sources on internal combustion engine

The main power source of modern electric start systems for internal combustion engines is an acid-lead battery. Existence chemical reactions, which occur in between battery electrolyte and lead plates may be causes problems with it exploitation. For a many reasons, its operation requires a lot of labor, especially in cold conditions. In this regard, it was proposed to use a capacitor system electric supply taking in view its discharge characteristics. Electrolytic capacitors and supercapacitors are sources of temporary charge storage and have optimal properties for their use in the engine start system as a partial displacement of the acid-lead battery, against the background of its some negative qualities. The article deals with the evaluation and comparison of the electric motor start system from capacitors and supercapacitors, as well as the possibility of their implementation on a mobile machine equipped with ICE.

Prerequisites and prospects for the development of novel systems based on the Keplerate type polyoxomolybdates for the controlled release of drugs and fluorescent molecules

Synthetic approaches were proposed to the development of hybrid organic—inorganic systems based on giant Keplerate polyoxometalates (POM Mo132), biocompatible polymers, and fluorescent molecules. A concept was formulated for the production of new systems for the prolonged release of drugs bearing a constant or temporary (protonated group) positive charge and fluorescent labels for tissue staining during electrophoretic introduction. In particular, a possibility of covalent functionalization of the POM Mo132 surface by the organosilicon molecules (aminopropyltrimethoxysilane) was shown. A promising procedure of the synthesis of NHS-esters of rhodamine B for the subsequent inclusion into the hybrid system was developed. The kinetic studies of POM destruction in an aqueous medium were carried out. The influence of association of rhodamine B with Mo132 on the character of fluorescence was studied.

Communal Acts of IoT Consumers: A Potential Threat to Security and Privacy

Consumer Electronics Internet of Things (CEIoT) products, implemented with improper security measures and inadequate privacy-preserving mechanisms, let the hackers or intruders to access and misuse consumer's personal information. In this paper, we present a framework and perspective to study and address Internet of Things (IoT) consumer's security and privacy violation from seemingly five different angles; borrow, rent, gift, resale, and retire. In the act of borrow, an IoT consumer takes and uses another consumer's CEIoT products with the intention of return after usage. In the act of rent, a consumer offers his CEIoT products to other people for temporary usage and charges regular payment for the service. In the act of gift, a consumer willingly gives or presents his used CEIoT products to his friends or relatives without payment. In the act of resale, IoT consumers sell their previously bought or used CEIoT products. In the act of retire, IoT consumers dispose of or throw their used CEIoT products when they become out of service or after the end of product's life. This act could raise serious privacy concerns, since “IoT waste” may become an attractive gateway for cybercriminals to access private information. Moreover, we also present challenges with the above-mentioned five acts of security and privacy violation. And finally, we suggest some recommendations to preserve the security and privacy of IoT consumers.

Lab product prices hit by China tariffs

Major suppliers of laboratory equipment and consumables are increasing prices or shifting production away from China in response to the ongoing trade dispute between the US and China. Cole-Parmer is the latest research supply house to increase prices because of tariffs China has imposed during the trade standoff. The firm sent a letter to US customers at the end of 2018 telling them to expect price increases effective Jan. 3. Until now, a spokesperson points out, the firm hasn’t increased prices and mostly satisfied customers with stock obtained prior to US imposition of a 10% tariff on Chinese goods in September. China followed with similar tariffs on US goods. But now that Cole-Parmer is restocking at higher prices because of the tariffs, it will include a temporary charge on invoices to recover tariff costs, the spokesperson says. While the US and China are in talks to settle the dispute, further

Preparation and characterization of a piezoelectric poly (vinylidene fluoride)/nanohydroxyapatite scaffold capable of naproxen delivery

Piezoelectric polymers are of great interest because of their ability to produce temporary surface electric charge, which can have a positive impact on the growth, attachment and proliferation of osteoblastic cells. The aim of this study was to combine potential osteoinductive properties of piezoelectric PVDF with the excellent bioactivity of nHA. In this regard, PVDF/nHA composite scaffolds were fabricated via a solvent casting/particulate leaching (SC/PL) method. The composite scaffold at 5 wt% nHA was annealed for 5 h at 60 °C and 90 °C in order to induce α to β phase transformation. Naproxen (NAP) was chosen as a reference drug and was complexed with beta-cyclodextrin (βCD) to form an inclusion complex (NAP-βCD-IC). Both NAP and NAP-βCD-IC were incorporated into PVDF solution during the fabrication process. The results showed that pore size and porosity both increased with the addition of nHA up to 5 wt%. The compressive modulus and strength of the scaffolds was increased with increasing nHA content in the composite. Fourier transform infrared (FTIR) spectroscopy confirmed increased β phase content due to annealing, and a higher increment was achieved for samples annealed at 90 °C. Superior cell viability was observed in the sample with a higher amount of piezoelectric β phase compared with the as-prepared sample and the sample annealed at 60 °C. The release profile of NAP from the PVDF/nHA composite scaffold showed that the formation of NAP-βCD inclusion complexes increased the rate and amount of NAP release from the scaffold.

Experimental evidence of electron capture and emission from trap levels in Cz silicon

Up to now the existence of trap levels − defect levels in the forbidden band gap which temporary trap minority charge carriers − in Cz silicon was controversially discussed. We directly monitor the transient dynamics of the free electron density in the conduction band by the means of a time correlated single photon counting of photoluminescence. A variation of the experimental conditions reveals both a decrease of the electron density on a timescale of microseconds, which is not governed by recombination and an apparent generation of electrons on a scale of up to multiple seconds. We discuss that the transient dynamics may be excellently described by trap levels, providing strong evidence for their existence.

Recent Advances in Understanding Delayed Photoluminescence in Colloidal Semiconductor Nanocrystals

Colloidal semiconductor nanocrystals display remarkably bright, strongly size-dependent photoluminescence properties. Following photoexcitation of these materials, temporary charge carrier separation can occur where one or both charge carriers are trapped. Charge detrapping can reform the emissive state on long time scales up to seconds, causing delayed luminescence. This delayed luminescence has not yet been thoroughly explored, and appears to be closely associated with a phenomenon observed at the single particle level, i.e. photoluminescence intermittency (blinking). Here, some of our recent work on the delayed luminescence properties of nanocrystals of different chemical composition is reviewed. These results provide insight into the mechanism of carrier detrapping, and are discussed in the context of photoluminescence blinking.

Efficient photoelectrochemical water splitting on ultrasmall defect-rich TaOx nanoclusters enhanced by size-selected Pt nanocluster promoters.

Formation of nanoclusters has attracted a lot of attention in recent years because of their distinct properties from isolated atoms and bulk solids. Here, we focus on the catalytic properties of supported transition metal oxide nanoclusters, such as TaO2, with a well-defined size distribution below 10 nm. We show that their catalytic performance can be greatly enhanced by introducing a reaction promoter such as Pt. Different combinations of precisely size-selected, defect-rich TaOx and Pt nanoclusters are produced by a gas-phase aggregation technique in a special DC magnetron sputtering system. Argon flow rate and aggregation length are carefully optimized to control the sizes of these ultrasmall TaOx and Pt nanoclusters by using a quadrupole mass filter, and TEM studies reveal the different crystalline nature of TaOx (amorphous) and Pt (crystalline) nanoclusters. We have further demonstrated the size-dependent photoanode activity of (TaOx, Pt) nanocluster systems in a photoelectrochemical water splitting reaction, where the Pt nanocluster promoters are found to provide a significant enhancement in the photocurrent density, approximately tripled that was observed from just TaOx nanocluster catalysts alone. The photocurrent density and photoconversion efficiency tend to reduce when Pt nanoclusters become overpopulated due to blocking of the photosensitive TaOx surface. Reducing the Pt nanocluster size resolves this problem by incorporating a greater number of smaller nanocluster promoters without blocking TaOx, which leads to further enhancement in the photocurrent density. The enhanced photocatalytic activity is attributed to synergetic effects introduced by the Pt nanoclusters that act as temporary charge storage sites to facilitate effective separation of a large number of electron-hole pairs, generated from a large number of active sites on the defect-rich amorphous TaOx nanoclusters upon illumination.

Neat Little Packages

This study presents different researches on developing genetic medicines and efficient engineered delivery systems. Researchers have developed a range of approaches to deliver cancer drugs. Many of these techniques would adapt easily for genetic medicine. In fact, many researchers are already putting them to work. Arcturus Therapeutics in San Diego, a ribonucleic acid (RNA) medicines company, is working on development of an advancement over previous lipid-based delivery systems. Arcturus’s solution is a biodegradable lipid with a temporary charge, just enough to wrap medicines and RNA in a loose, yarn-like bundle. When the bundle reaches the targeted cell, the cell engulfs it, trapping it in a small sac that travels into the cell. As engineers test the design of delivery systems, they will find themselves working with scientists to understand how all the pieces fit together. Experts foresee that clinics in 30 years from the present will sequence patients’ genomes and biopsy their conditions, and prescribe treatments that target the precise cause of disease.

Surface reactions and structural evolution of organosilicate glass under Ar plasma bombardment

Ab initio molecular dynamics (AIMD) simulations with a variable time step setup were used to investigate collision reactions, collision cascades and subsequent structural changes of organosilicate glass (OSG) low-k dielectric surfaces under Ar plasma bombardment with kinetic energies up to 100eV. Reactions that result in carbon loss and glass network structure changes during plasma treatment were carefully examined, since carbon loss increases the dielectric constant of the low-k dielectrics and the susceptibility to water attack, thus adversely affecting the performance of these dielectric materials in microelectronic devices. Results from AIMD based collision cascade simulations have provided mechanistic understanding of collision reactions during plasma bombardment. It was found that Si–CH3 bond scission and CH3 abstraction reactions are the primary methods of carbon loss. Two distinct mechanisms were identified for CH3 removal from 100eV plasma bombardment, one due to direct momentum transfer from the high-energy incident Ar atom to a Si–O bond on the OSG surface, and the other due to generation of highly reactive atomic oxygen radicals during collision cascades. Atomic oxygen radicals generated during cascades were found to occur at a rate of 1–3 per 100eV Ar impact with radical kinetic energies ranging from 2.2 to 42.6eV, well above the minimum energy of 0.1eV for Si–CH3 bond breakage. Both reaction mechanisms were examined through atomic charge analysis and the results indicated that the Ar atom ionizes when it impacts the OSG surface, causing temporary charge transfer from the Ar atom to the Si–O bond and playing a role in CH3 removal. The cascading atomic oxygen radicals and the ionization of the Ar atom during the Si–CH3 bond scission and CH3 removal demonstrate the secondary effects of Ar bombardment which must be considered during plasma etching of low-k dielectrics.

Simulations of ion guiding through a straight macrocapillary: Interpretation of an experiment and comparison with nanocapillaries

The transmission of 4.5 keV ${\text{Ar}}^{7+}$ ions through a straight cylindrical macrocapillary is simulated in accordance with the results of a recent experiment. A detailed comparison with the results for nanocapillaries is performed. The theoretical method is based on a code previously developed for a nanocapillary. The ion trajectories are affected by the electric field originating from the charges previously deposited on the capillary wall. The tilt angle of the capillary axis relative to the incident beam was varied within ${\text{0}}^{\ensuremath{\circ}}$--${\text{5}}^{\ensuremath{\circ}}$. Both the surface conductivity along the capillary wall and the conductivity into the capillary bulk were treated, providing clear evidence that the bulk conductivity is dominant, involving essentially a linear field dependence. By variation of this conductivity the mechanisms for the major experimental observations were revealed. At low conductivity the fluctuations of the mean ion emission angle are explained by the overloading of temporary charge patches, which are missing at high conductivity. Moreover, it is shown that the capillary guiding power decreases with increasing conductivity, in agreement with the experimental results.

Angstrom-resolved real-time dissection of electrochemically active noble metal interfaces.

Electrochemical solid|liquid interfaces are critically important for technological applications and materials for energy storage, harvesting, and conversion. Yet, a real-time Angstrom-resolved visualization of dynamic processes at electrified solid|liquid interfaces has not been feasible. Here we report a unique real-time atomistic view into dynamic processes at electrochemically active metal interfaces using white light interferometry in an electrochemical surface forces apparatus. This method allows simultaneous deciphering of both sides of an electrochemical interface-the solution and the metal side-with microsecond resolution under dynamically evolving reactive conditions that are inherent to technological systems in operando. Quantitative in situ analysis of the potentiodynamic electrochemical oxidation/reduction of noble metal surfaces shows that Angstrom thick oxides formed on Au and Pt are high-ik materials; that is, they are metallic or highly defect-rich semiconductors, while Pd forms a low-ik oxide. In contrast, under potentiostatic growth conditions, all noble metal oxides exhibit a low-ik behavior. On the solution side, we reveal hitherto unknown strong electrochemical reaction forces, which are due to temporary charge imbalance in the electric double layer caused by depletion/generation of charged species. The real-time capability of our approach reveals significant time lags between electron transfer, oxide reduction/oxidation, and solution side reaction during a progressing electrode process. Comparing the kinetics of solution and metal side responses provides evidence that noble metal oxide reduction proceeds via a hydrogen adsorption and subsequent dissolution/redeposition mechanism. The presented approach may have important implications for designing emerging materials utilizing electrified interfaces and may apply to bioelectrochemical processes and signal transmission.

Recollections of My Time in Malaya (1945–1956) Part 2

Recollections of My Time in Malaya (1945–1956) Part 2 * J. M. Gullick Jelebu The Jelebu district, shut off behind a range of hills and isolated from the rest of Negri Sembilan, was comparatively unimportant. We had no one to send there and for a week or two after our first arrival it was left to its own devices. However, two items of news from Jelebu brought it to attention. First, the Undang of Jelebu, Dato’ Abdullah, had died—from natural causes and at a considerable age—in August 1945. It would be necessary to elect a successor without the long period of wrangling, which usually delayed such an election for months or even years, as the new Undang would be required as one of the necessary signatories to the treaty that MacMichael would bring to Negri Sembilan in November. Secondly, the local MPAJA, deeply suspicious of the local administration, had removed all the records, including the essential land registers, from the District Office and had destroyed them. This was a serious blow to the machinery of administration (though throughout Malaya the land registers were closed and would remain so for months). As there was no one else available, Calder asked me to visit Jelebu and take temporary charge in addition to my duties in Seremban. I set off on 23 September 1945. The roads throughout Negri Sembilan were in surprisingly good condition. The Japanese had not done much to maintain them, but the pre-war PWD had done a good job. I had no difficulty in getting the aged Humber Hawk which I used for my journeys up the steep and winding road to the Bukit Tangga pass. At the top I paused to admire the magnificent view of Negri Sembilan stretching away to the Malacca Strait—everyone pauses there, including the dozen police who were to be ambushed by the MPAJA and massacred there in December 1949. At Kuala Klawang, the district headquarters, I found the Malay District Officer (I think his name was Baba) at his house. We went together to the District Office, which was literally stripped clean of every scrap of paper it had ever contained. I remember that when I asked the DO for a list of his staff I had to tear a leaf from my notebook so that he could write the names on it. He was quite positive that the MPAJA had burnt the missing land registers. The Japanese had used the District Office as their headquarters and the MPAJA had deemed it necessary to destroy everything in it in case it should be Japanese. This was the second major loss of records suffered in Negri Sembilan at this time; the other was the loss of the greater part of the State Secretariat files in Seremban. In that case the Kempeitai, who had used part of the building, sent a military fatigue party under a sergeant to burn their records before the arrival of British troops, and the [End Page 53]sergeant, uncertain as to what was intended, burnt almost everything in that wing of the Secretariat building—again a pointless destruction of irreplaceable records. To return to Jelebu—it was plain that the entire district administration had come to a halt and the District Officer was obviously very apprehensive for his own safety. Kuala Klawang itself is a small trading centre, and the main Chinese settlement is Titi, a tin-mining centre a few miles away. I felt that I should see—and be seen at—Titi. So the DO, protesting faintly, got into the car and we went off to Titi. Here the MPAJA were established at the police station and were flying their ‘Tiga Bintang’ flag (3 stars—one for each of the main communities of Malaya) at the flagpole. L. K. L. Siaw in his Chinese Society in Rural Malaysia: A Local History of the Chinese in Titi, Jelebu, published in 1983 almost 40 years after these events, presumably relied on local Titi traditions—somewhat vainglorious—in describing the foundation of a communist republic at Titi which remained defiant until the arrival of a battalion of British troops brought it to an end. This is pure fiction...

Self-limiting droplet fusion in ionic emulsions.

We make an oil-in-water emulsion, which is initially stabilized using a first ionic surfactant, and mix it with a solution of a second ionic surfactant having the opposite charge, thereby inducing massively parallel droplet fusion. A transient disruption of the screened-charge repulsive barrier between interacting droplets, caused by the second ionic surfactant, arises from significant yet temporary charge neutralization of the first ionic surfactant on the surfaces of the oil droplets while mixing occurs. Interestingly, if a moderate molar excess of one surfactant exists, then the resulting emulsion re-stabilizes after limited droplet fusion. By adjusting the droplet volume fraction, concentrations of first and second surfactants, and volumes of the emulsion and the solution of the second surfactant, we control the degree of droplet coalescence and achieve a self-limiting droplet fusion process. Using optical microscopy, we observe that flat, thin, crystalline films can form between the two oil compartments after fusion of two or more immiscible microscale droplets. However, no such crystalline films are seen on the highly curved oil-oil interfaces inside nanoscale droplets that are composed of two or more immiscible oils and have been fused in the same manner, as revealed by cryogenic transmission electron microscopy.