Nice Correlation Research Articles

The effect of ligand basicity on the unconventional hydrogen-bond in H(μ-H)Os 3(CO) 10L (L=amine) derivatives

The reaction of amine ligands with the unsaturated 46 e − cluster Os 3(μ-H 2)(CO) 10 yields a series of complexes of formula Os 3H(μ-H)(CO) 10(amine). In these derivatives the presence of an unconventional hydrogen-bond MH⋯HN is detected by the evaluation of proton spin-lattice relaxation times. In order to elucidate the relationship between p K b and H⋯H length, the MH⋯HN distances were quantified for amines of known p K b. In practice, this was achieved by comparing the T 1 values of the terminal hydride resonances of the protonated isotopomer with the T 1 values of the corresponding derivative containing selectively deuterated amine. A nice correlation between the MH⋯HN distances and the p K b of the amine ligands was found. DFT calculations were carried out for the cluster on Os 3H(μ-H)(CO) 10(Benzylamine) to gain a fuller understanding of the possible coordination geometries of an amine ligand on the surface of a tri-osmium cluster.

Electronic determinants of photoacidity in cyanonaphthols.

We present semiempirical AM1 calculations for the ground and excited state of 2-naphthol and some of its cyano derivatives in the gas phase. Following photoexcitation, the Mulliken electron density on the oxygen diminishes slightly for the acid and more conspicuously for the anionic conjugated base. This agrees with the measured solvatochromic parameters for 2-naphthol. In both electronic states, we find a nice correlation with the measured pK values in water. The electronic charge distribution on the distal ring of the anion agrees with the experimental acidity order in both S(0) and S(1). Upon excitation, it increases predominantly in positions 3, 5, and 8. The ring system of the anion assumes an alternate quinoidal structure in the ground state of the anion, which becomes more symmetric in the relaxed excited state. This suggests that the enhanced aromatic character of a 4n electron system in the excited state allows for better delocalization of the oxygen charge within the ring.

Protein kinase inhibitors and the dynamics of tight junction opening and closing in A6 cell monolayers.

This study focuses, in A6 cell monolayers, on the role of protein kinases in the dynamics of tight junction (TJ) opening and closing. The early events of TJ dynamics were evaluated by the fast Ca++-switch assay (FCSA), which consisted of opening the TJs by removing basolateral Ca++ (Ca++(bl)), and closing them by returning Ca++(bl) to normal values. Changes in TJ permeability can be reliably gauged through changes of transepithelial electrical conductance (G) determined in the absence of apical Na+. The FCSA allows the evaluation of the effects of drugs and procedures acting upon the mechanism controlling the TJs. The time courses of TJ opening and closing in response to the FCSA followed single-exponential time courses. A rise of apical Ca++ (Ca++(ap))causes a reduction of TJ opening rate in an FCSA or even a partial recuperation of G, an effect that is interpreted as mediated by Ca++(ap) entering the open TJs. Protein kinase C (PKC) inhibition by H7 at low concentrations caused a reduction of the rate of junction opening in response to Ca++(bl) removal, without affecting junction closing, indicating that PKC in this preparation is a key element in the control of TJ opening dynamics. H7 at 100 microm completely inhibits TJ opening in response to Ca++(bl) withdrawal. Subsequent H7 removal caused a prompt inhibition release characterized by a sharp G increase, a process that can be halted again by H7 reintroduction into the bathing solution. Differently from the condition in which Ca++ is absent from the apical solution, in which H7 halts the process of G increase in response to a FCSA, when Ca++ is present in the apical solution, addition of H7 during G increase in an FCSA not only induces a halt of the G increase but causes a marked recuperation of the TJ seal, indicated by a drop of G, suggesting a cooperative effect of Ca++ and H7 on the TJ sealing process. Staurosporine, another PKC inhibitor, differently from H7, slowed both G increase and G decrease in an FCSA. Even at high concentrations (400 nm) staurosporine did not completely block the effect of Ca++ withdrawal. These discrepancies between H7 and staurosporine might result from distinct PKC isoforms participating in different steps of TJ dynamics, which might be differently affected by these inhibitors. Immunolocalizations of TJ proteins, carried out in conditions similar to the electrophysiological experiments, show a very nice correlation between ZO-1 and claudin-1 localizations and G alterations induced by Ca++ removal from the basolateral solution, both in the absence and presence of H7.

Photophysics of pyridylporphyrin Ru(II) adducts: heavy-atom effects and intramolecular decay pathways.

Eight adducts between different pyridylporphyrins and ruthenium complexes, MPyP[RuCl(2)(DMSO)(2)(CO)], c-DPyP[RuCl(2)(DMSO)(2)(CO)](2), TrPyP[RuCl(2)(DMSO)(2)(CO)](3), TPyP[RuCl(2)(DMSO)(2)(CO)](4), (MPyP)(2)[RuCl(2)(DMSO)(2)], [c-DPyP[RuCl(2)(DMSO)(2)]](2), MPyP[RuCl(2)(CO)(3)], and [c-DPyP[RuCl(2)(CO)(2)]](2), have been investigated. The results show that in all the adducts the porphyrin singlet is quenched, to a greater or lesser extent, relative to the parent-free molecule. This study provides insight into the mechanisms of singlet quenching in the adducts. Two mechanisms for singlet quenching, both related to the "heavy-atom effect" of the ruthenium center and experimentally distinguishable by transient spectroscopy, are examined. Enhanced intersystem crossing within the porphyrin chromophore is demonstrated for the series of adducts MPyP[RuCl(2)(DMSO)(2)(CO)], c-DPyP[RuCl(2)(DMSO)(2)(CO)](2), TrPyP[RuCl(2)(DMSO)(2)(CO)](3), and TPyP[RuCl(2)(DMSO)(2)(CO)](4), where a nice correlation is observed between the magnitude of the effect and the number of ruthenium centers attached to the pyridylporphyrin chromophore. Singlet-triplet energy transfer from the pyridylporphyrin chromophore to the ruthenium center(s) is an additional efficient quenching channel for adducts containing ruthenium centers with weak field ligands and low triplet energies, such as (MPyP)(2)[RuCl(2)(DMSO)(2)] and [c-DPyP[RuCl(2)(DMSO)(2)]](2).

A Low-Cost Dynamic Surface Tension Meter with a LabVIEW Interface and Its Usefulness in Understanding Foam Formation

Using standard chemical laboratory equipment, it is possible to construct a low-cost dynamic surface tension meter. The concept of the experiment seemed very appropriate to demonstrate a broad range of dynamic effects on surface tension. Everyday samples such as beer and cola revealed that the dynamic surface tension data are a very useful aid to understanding the foaming characteristics of these liquids. Further experiments into foam formation demonstrated that static surface tension data are useless in explaining such dynamic processes; on the other hand, a very nice correlation between dynamic surface tension and foam volume clearly indicated that the experimental setup presented in this paper is well suited to explaining the phenomena occurring at the surface of liquids during foam formation.

Quantification of liver iron concentration with magnetic resonance imaging by combining T1-, T2-weighted spin echo sequences and a gradient echo sequence

Background: The aim of the study was to quantify hepatic iron by MRI for practical use. Methods: In twenty-three patients with various degrees of iron overload, measurements were carried out with a 1.5 Tesla MR unit. A combination of pulse sequences (T1, T2 and gradient echo) enabled us to quantify smaller amounts of liver iron as accurately as larger amounts of liver iron. The gradient echo sequence provided us with a good correlation when detecting smaller amounts of iron in the liver where the T1 sequence provided a good correlation when larger amounts of iron were present. Results: The combination of the three sequences showed a nice correlation (r=−0.93, P<0.001) and provided us with an accurate estimate of the liver iron content (LIC). This correlation was achieved with a LIC from the lower range of normal up to LIC of 146 mmol/kg dry weight, which seems the highest measurable liver iron content for a 1.5 Tesla MRI. Measuring in the lower range makes it possible to decide whether further invasive diagnostic investigations by a liver biopsy are indicated. Conclusion: MRI is a useful tool to quantify iron overload non-invasively. In cases where a liver biopsy is hazardous MRI can easily be used to obtain reliable, quantitative information about the initial LIC. Quantification by MRI could also be used for follow up of the iron content during depletion treatment by phlebotomy or iron chelation. The stronger the magnet the more sensitive the detection of concentrations up to 150 mmol/kg is. A semi-quantitative judgement will only be possible with severe iron overload over 150 mmol/kg. If such an iron excess is found, a liver biopsy should be performed to exclude cirrhosis.

Ab initio theoretical optical rotations of small molecules

Abstract Optical rotations of small chiral molecules have been calculated ab initio to evaluate the role of substituents and of conformations. The optical rotations of oxaziridines provide a nice correlation between the sign of optical rotation and absolute configuration. Such correlation is not obvious in the case of diaziridines and tetrahydrofurans. The optical rotations obtained for different conformers of 3-butyn-2-ol suggested a possible predominant conformation in liquid solutions. The prediction of optical rotations, as a function of dihedral angle, for H 2 O 2 and H 2 S 2 reveal that the sign of optical rotation is negative for counter-clockwise dihedral angles (M-helicity) and the magnitude is maximum at a dihedral angle of 90° (in H 2 O 2 ) or 110° (in H 2 S 2 ).

Quantitative Brain SPECT and the NIH Stroke Scale

HomeStrokeVol. 29, No. 7Quantitative Brain SPECT and the NIH Stroke Scale Free AccessOtherPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessOtherPDF/EPUBQuantitative Brain SPECT and the NIH Stroke Scale Michael A. Meyer Michael A. MeyerMichael A. Meyer Department of Neurology, University of Missouri, Columbia, Missouri Search for more papers by this author Originally published1 Jul 1998https://doi.org/10.1161/01.STR.29.7.1480Stroke. 1998;29:1480To the Editor: The excellent article by Grotta and Alexandrov1 not only provides objective evidence in a small number of patients that intravenous tissue plasminogen activator (tPA) improves cerebral perfusion but also provides important data about the National Institutes of Health Stroke Scale (NIHSS) rating system. If the NIHSS score data from their article are plotted against the corresponding single-photon emission computed tomography (SPECT)-graded scale score, a relationship becomes apparent, as shown in the Figure. If one omits the 4 outlying points with high NIHSS scores with less-than-expected asymmetries on SPECT in this group of 21 SPECT scans, a fairly linear relationship is noted. Without these 4 pairs of outlying data, approximately 10 points of deficit on the NIHSS roughly correlates with 40 points on their SPECT-graded scale scoring system, which quantifies the severity and extent of asymmetries in cerebral perfusion over 4 SPECT slices.Rankin Scale scores at 1 month after stroke have been shown to correlate with the degree and size of hypoperfusion on SPECT scans of perfusion within 36 hours after symptom onset in a group of 55 patients.2 Whereas the baseline NIHSS score was found to have an overall accuracy of 83% in predicting 3-month outcome in a study of 373 acute stroke patients,3 more research is needed on the predictive value of quantitative SPECT and how it correlates with the NIHSS, Rankin Scale, and other functional outcome measurements. A firm correlation remains to be made between NIHSS and the degree and size of cerebral hypoperfusion in acute stroke; one or more SPECT indices of volume and severity of hypoperfusion may need to be considered.Download figureDownload PowerPoint Figure 1. National Institutes of Health Stroke Scale (NIHSS) score data from Grotta and Alexandrov1 plotted against the corresponding single-photon emission computed tomography graded scale (SGS) score. References 1 Grotta JC, Alexandrov A. tPA-associated reperfusion after acute stroke demonstrated by SPECT. Stroke.1998; 29:429–432.CrossrefMedlineGoogle Scholar2 LaLoux P, Richelle P, James J, DeCoster P, Laterre C. Comparative correlations of HMPAO SPECT indices, neurologic score, and stroke subtypes with clinical outcome in acute carotid infarcts. Stroke.1995; 26:816–821.CrossrefMedlineGoogle Scholar3 Muir KW, Weir CJ, Murray GD, Povey C, Lees KR. Comparison of neurological scales and scoring systems for acute stroke prognosis. Stroke.1996; 27:1817–1820.CrossrefMedlineGoogle ScholarstrokeahaStrokeStrokeStroke0039-24991524-4628Lippincott Williams & WilkinsResponseGrotta James, MD and Alexandrov Andrei, MD071998We thank Dr Meyer for his comments. We have also noted the nice correlation between the neurological status of the patient on arrival as measured by the baseline NIHSS and the perfusion defect as measured by SPECT. In evaluating the acute stroke patient, we all want a physiological test that is convenient, safe, inexpensive, widely available, and informative. SPECT fulfills many of these criteria. Perhaps clinical trials incorporating such studies will show that these tests can help us select our therapeutic strategies. However, until then, it is reassuring that in the first few hours after stroke onset, the neurological exam accurately reflects what is going on inside the brain physiologically. Previous Back to top Next FiguresReferencesRelatedDetailsCited By Oba S, Tohara H, Nakane A, Tomita M, Minakuchi S and Uematsu H (2016) Screening tests for predicting the prognosis of oral intake in elderly patients with acute pneumonia, Odontology, 10.1007/s10266-016-0238-5, 105:1, (96-102), Online publication date: 1-Jan-2017. Wilde E, McCauley S, Kelly T, Weyand A, Pedroza C, Levin H, Clifton G, Valadka A, Schnelle K, Shah M and Moretti P (2010) The Neurological Outcome Scale for Traumatic Brain Injury (NOS-TBI): I. Construct Validity, Journal of Neurotrauma, 10.1089/neu.2009.1194, 27:6, (983-989), Online publication date: 1-Jun-2010. Meyer M (2008) Stroke Quick Score: a visual aid in scoring neurologic deficits for acute stroke with National Institutes of Health Stroke Scale, The American Journal of Emergency Medicine, 10.1016/j.ajem.2007.04.027, 26:2, (189-190), Online publication date: 1-Feb-2008. Van Laere K and Zaidi H (2006) Quantitative Analysis in Functional Brain Imaging Quantitative Analysis in Nuclear Medicine Imaging, 10.1007/0-387-25444-7_14, (435-470), . Odderson I (1999) The National Institutes of Health Stroke Scale and Its Importance in Acute Stroke Management, Physical Medicine and Rehabilitation Clinics of North America, 10.1016/S1047-9651(18)30162-1, 10:4, (787-800), Online publication date: 1-Nov-1999. Beaulieu C, De Crespigny A, Tong D, Moseley M, Albers G and Marks M (2001) Longitudinal magnetic resonance imaging study of perfusion and diffusion in stroke: Evolution of lesion volume and correlation with clinical outcome, Annals of Neurology, 10.1002/1531-8249(199910)46:4<568::AID-ANA4>3.0.CO;2-R, 46:4, (568-578), Online publication date: 1-Oct-1999. July 1998Vol 29, Issue 7 Advertisement Article InformationMetrics Copyright © 1998 by American Heart Associationhttps://doi.org/10.1161/01.STR.29.7.1480 Originally publishedJuly 1, 1998 Keywordsstroke assessmenttomography, emission computedPDF download Advertisement

TBIS measurements performed by MOKE for the study of soft ferromagnetic thin films and sandwiches: In-plane and biaxial anisotropies, local anisotropy and dispersion

Magneto-optic effects have been proved to be a premier tool for the study of magnetic thin films. In the case of films thinner than 1000 Å and if there is no appreciable variation of the magnetic structure through the thickness, the magneto-optic effects provide complete information. It is noteworthy that transverse biased initial susceptibility (TBIS) measurement is very sensitive, for it allows a precise determination of the anisotropy field and, moreover, to quantify the anisotropy dispersion distinguishing between short- and long-range magnetization fluctuations in the plane of the film the origin of which is different. If the samples are deposited on glass substrates, by performing TBIS measurements with a magneto-optic transverse Kerr effect (MOKE) we can obtain information of the processes occurring at both film/air and glass/film interfaces, providing information of the variation of the magnetic properties through the thickness. We have successfully applied this technique for the study of thin films and sandwiches, focusing our attention on the following items: 1. (1) Uniaxial in-plane anisotropy, local anisotropy and anisotropy dispersion in transition metal-rare-earth thin films. We have investigated the dependence of the uniaxial anisotropy and its dispersion on the rare-earth substituted and on the composition. Using the ripple theory we have evaluated the local anisotropy as a function of the rare-earth content, and we have found a very nice correlation between macroscopic and local anisotropies, allowing us to establish the origin of the macroscopic anisotropy in these alloys. 2. (2) TBIS measurements can also be used as an alternative technique to measure perpendicular anisotropy. We have developed a theoretical model to explain the particular behaviour of TBIS curves in the most general case when both in-plane and perpendicular anisotropies are present (biaxial anisotropy). From the fit of the experimental curves to the theoretical model we can obtain the in-plane and the perpendicular anisotropy fields. 3. (3) When the samples are not magnetically homogeneous, they may present different magnetic phases which may be made evident by our technique. 4. (4) We recently extended this technique to the study of ferromagnetic double-layered and sandwiched films. In these systems the magnetic and magneto-optical properties are strongly influenced by the coupling at the interfaces. The high sensitivity of our procedure allowed us to distinguish between two contributions to the anisotropy dispersion in sandwiched films: a well-known term due to the in-plane anisotropy skew (long-range fluctuations of the in-plane easy axis) and a contribution due to the existence of a weak perpendicular anisotropy.

Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) Measurements in the Diagnosis of Growth Hormone Insufficiency and Comparison with IGF-I Measurements

To analyze the utility of insulin-like growth factor binding protein-3 (IGFBP-3) radioimmunoassay in the diagnosis of GH insufficiency (GHI) and compare the results of IGFBP-3 and IGF-I, we measured IGF-I and IGFBP-3 in sera from normal children (n=309), short children (n=99) and patients with GHI (n=73). We divided the GHI group into two groups (complete and partial GHD) and divided all the patients into two groups depending upon age (less than and older than 10 years).The sensitivity of IGF-I for complete GHD (cGHD) was 80%, while the specificity for normal short children (NS) was 81%. The sensitivity of IGFBP-3 for cGHD was 93%, while the specificity for NS was 88%. In contrast, the sensitivities of IGF-I and IGFBP-3 for partial GHD (pGHD) were both only 43%. The poor discrimination between patients with pGHD and NS by using these two parameters may be the result of their relatively similar GH level, as compared to cGHD, or of the limitations of GH stimulation tests in the diagnosis of GHI.The specificities of IGF-I and IGFBP-3 for NS were high (82-92%) in children of all ages. The sensitivity of IGF-I for GHD at less than and older than 10 years old was 66% and 71%, respectively. The sensitivity of IGFBP-3 for GHI was good for children less than 10 years of age (84%) but poor for children older than 10 years (64%), because IGFBP-3 levels may also increase during puberty by mechanisms independent of the GH-IGF-I axis. Thus, in the younger chil-dren, the sensitivity for GHI of IGFBP-3 was higher than that of IGF-I.Finally, although nice correlation was observed between IGFBP-3 and IGF-I levels, some patients (both GHI and NS) had discordant results of IGFBP-3 and IGF-I either below or above the cutoff levels, possibly due to limitations of GHI diagnosis based upon GH stimulation tests.

Spectroscopic studies of Wolf-Rayet stars. IV - Optical spectrophotometry of the emission lines in galactic and large Magellanic Cloud stars

view Abstract Citations (178) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic Studies of Wolf-Rayet Stars. IV. Optical Spectrophotometry of the Emission Lines in Galactic and Large Magellanic Cloud Stars Conti, Peter S. ; Massey, Philip Abstract We present spectrophotometry of the leading emission-line features for nearly all the Wolf-Rayet stars in the Galaxy and in the Large Magellanic Cloud (LMC). These form the empirical basis of the normal relationships among the various lines. Emission lines have a wide range of strengths, but all lines in a given star are strong or weak together, aside from the well-understood ionization effects. We present the first extensive data of the N IV λ3480 feature in WN stars. This line persists to earlier types than does the singlet N IV λ4057 line, probably due to decreasing optical depth in the latter transition. Among those very few WN stars with anomalous lines, there are eight objects, mostly single stars, with inordinately strong C IV; we label them "WN/WC" and suggest that they have a "transition" composition between the WN and WC subclasses. We give quantitative descriptions of "early" (WNE; WCE) and "late" (WNL; WCL) types for the WN and WC classes, respectively. Among WC stars, the persistence of the C III λ4650 feature to the earliest subtypes (where C III λ5696 has already disappeared) suggests the importance of the contribution of C IV λ4658 to the blend, or an anomalous triplet-singlet behavior in the C III ions similar to that observed in N IV in the WN sequence. We compare the emission-line fluxes of He II λ4686 with the M_v_ for the WN stars of the LMC. Aside from the ionization effects, there is a nice correlation of these parameters since brighter stars have more continuum flux present at 4686 A. Although WCL stars have not been found in the LMC, the line strengths of the other W-R stars are very similar in that system and in our own Galaxy. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/167101 Bibcode: 1989ApJ...337..251C Keywords: Emission Spectra; Magellanic Clouds; Optical Emission Spectroscopy; Stellar Spectrophotometry; Wolf-Rayet Stars; Abundance; Helium; Line Spectra; Statistics; Tables (Data); Astrophysics; GALAXIES: MAGELLANIC CLOUDS; SPECTROPHOTOMETRY; STARS: STELLAR STATISTICS; STARS: WOLF-RAYET full text sources ADS | data products SIMBAD (148) Related Materials (5) Part 1: 1983ApJ...268..228C Part 2: 1984ApJ...280..181T Part 3: 1986ApJ...300..379T Part 5: 1989ApJ...341..113C Part 6: 1990ApJ...354..359C

Calculation of activity coefficients from a novel numerical solution of the Poisson–Boltzmann equation and application to 23Na NMR of sodium polystyrene sulfonate

Interaction of sodium cations with polystyrene sulfonate (PSS) is studied. The Poisson–Boltzmann equation, modified in order to incorporate ion–ion correlation, is solved numerically using a cell model. Outstanding agreement is found between the calculated and measured activity coefficients γ± for systems consisting of NaPSS+NaCl, KPSS+KCl, CaPSS+CaCl2, and the more complex system, the quarternary mixture NaPSS+CaPSS+NaCl+CaCl2. A complementary study by sodium-23 NMR provides a reliable estimate of the fractions of bound, atmospherically condensed, and free sodium ions for NaPSS in the presence of added NaCl, HCl, MgCl2, and MnCl2. We find a nice correlation (ρ = 0.93, N = 16) between the observed 23Na line broadenings and the calculated electrostatic field gradients for these various cases.

Mutagenicity and K-region reactivity of monomethyl derivatives of benz(a)anthracene in a self-consistent-field molecular orbital theory

The relative mutagenicities of the monomethyl derivatives of benz(a)anthracene have been studied on the basis of their K-region reactivities as obtained from a suitable self-consistent-field molecular orbital theory for the mobile π-electrons. Barring a few specific cases of these monomethyl derivatives, a nice correlation between the mutagenicities and the K-region reactivities has been obtained.

Kentromorphic phases in three species of Phasmatodea.

Nymphs of the injurious Australian Phasmatidae Podacanthus wilkinsoni Macl., Didymuria violescens (Leach), and Ctenomorphodes tessulata (Gray) were reared from the early instars in crowds and in isolation. Typical kentromorphic phase differences, quite analogous to those of locusts, developed in the colour pattern of the isolated and crowded insects and persisted into the adult stage. This is believed to be the first record of kentromorphic phases in the Phasmatodea. The two types of pattern are described and illustrated in colour. The "lowdensity phase" is rather uniform and usually green, while the "high-density phase" is conspicuously patterned with black, yellow, and sometimes white. The extreme conditions are connected by all intergrades and for Podacanthus a rating scale has been used to measure the phase level attained by individual insects. Observations were made on the mean phase rating corresponding to different densities of Podacanthus nymphs on eucalypt saplings in the field. The rating rose from about 1.5 at densities of one insect per 10-20 15-in. branchlets to the scale maximum of 4.0 at densities of about one insect per branchlet. A correlation was also found between the ratings of museum specimens and subjective estimates of abundance recorded by their collectors. All three species showed morphometric phase differences also analogous to those of locusts: the length of femur III, the ratio length of femur III/width of head, and the sexual dimorphism with respect to width of head all tended to lower values in the high-density phase. The phasmatids showed no overt gregariousness and Podacanthus nymphs spent 95 per cent, of their time at rest, even in crowds of the high-density phase. Thus, in this group, activity and gregariousness can play no part in phase change. It is therefore probable that, both here and in locusts, the physiological mechanism of pattern change involves a direct nervous link between sensory stimulation and the endocrine system responsible for the pigmentation. Neither Uvarov's nor Kennedy's theory regarding the biological function of phase pattern change is applicable to the Phasmatidae and it must be doubted that either is applicable to locusts. It is suggested that the colour-pattern aspect of kentromorphic variation may be a mechanism for effecting a switch-over from procryptic to aposematic adaptations in nice correlation with the population densities under which each of these has survival value.