Outer Defect Research Articles

Development and Integration of the Ear.

The perception of our environment via sensory organs plays a crucial role in survival and evolution. Hearing, one of our most developed senses, depends on the proper function of the auditory system and plays a key role in social communication, integration, and learning ability. The ear is a composite structure, comprised of the external, middle, and inner ear. During development, the ear is formed from the integration of a number of tissues of different embryonic origin, which initiate in distinct areas of the embryo at different time points. Functional connections between the components of the hearing apparatus have to be established and maintained during development and adulthood to allow proper sound submission from the outer to the middle and inner ear. This highly organized and intimate connectivity depends on intricate spatiotemporal signaling between the various tissues that give rise to the structures of the ear. Any alterations in this chain of events can lead to the loss of integration, which can subsequently lead to conductive hearing loss, in case of outer and middle ear defects or sensorineural hearing loss, if inner ear structures are defective. This chapter aims to review the current knowledge concerning the development of the three ear compartments as well as mechanisms and signaling pathways that have been implicated in the coordination and integration process of the ear.

Pattern of Macular Ganglion Cell-Inner Plexiform Layer Defect Generated by Spectral-Domain OCT in Glaucoma Patients and Normal Subjects.

To elucidate patterns of macular ganglion cell-inner plexiform layer (GCIPL) defects by Cirrus optical coherence tomography (OCT) and examine the spatial relationship between GCIPL defect and visual field (VF) defect patterns. A total of 116 eyes of 116 normal subjects and 111 eyes of 111 glaucoma patients were included. The 227 study subjects underwent Cirrus OCT imaging in macular cube mode and reliable standard VF testing. Two ophthalmologists blindly classified GCIPL defect patterns and VF defects. The frequency distribution of GCIPL defect patterns and spatial relationships between GCIPL defects and VF defects were investigated. GCIPL defect patterns were classified as minimal, inner, outer, diffuse mild, diffuse severe, inferior confined, inferior dominant, superior confined, and superior dominant defects in normal controls (71.6%, 7.8%, 4.3%, 1.7%, 0%, 10.3%, 1.7%, 1.7%, and 0.9%, respectively) and in glaucoma patients (11.7%, 3.6%, 4.5%, 7.2%, 21.6%, 22.5%, 18.0%, 4.5%, and 6.3%, respectively). In mild and moderate glaucoma patients, the inferior confined type was most frequent (21.9% and 50.0%, respectively). However, the diffuse severe type was most frequent (59.1%) in advanced glaucoma patients. The locations of the VF defects corresponded to the locations of the GCIPL defects in glaucoma patients (P=0.012). Glaucomatous damage of the macula was common and more frequent in the inferior retina. GCIPL defect patterns as determined by SD-OCT imaging corresponded well with central VF defects. It seems macular GCIPL analysis may be useful for evaluating glaucomatous optic neuropathy.

The Effect of Exposure of Mulberry to Acid Rain on the Defects Cocoon of Bombyxmori L

Air pollution may be indicated by the higher acid rain. Air pollution caused by the burning of fossil fuels increase emissions of SOx,NOx, and CO2 which can ultimately lead to acid rain. Exposure of acid rain may affect the cultivation of mulberry and the quality of silkworm cocoon. The aim of this research was to determine the effect of mulberry plants that have been exposed to acid rain to the percentage of cocoon defects and type of defects in C-301 and BS-09 races of Bombyxmori L. Acid rain that to applied on mulberry plant for 5 weeks was a modification of acid rain that occurred in Sidoarjo East Java, Indonesia. A total of 720 individuals of newly hatched silkworm were used in early research. Larvae fed by mulberry leaves that had been treated with artificial rain water in different levels of pH, i.e. pH's of 7.0 (well water as control), 6.2 (normal rain), and 4.6 (acid rain). Cocoon defects and type of cocoon defect were observed. Data were analyzed using multivariate ANOVA. The results showed that the treatments had no significant effect (P >0.05) on defective cocoon percentage. Treatment of pH 7.0, 6.2, 4.6 had defective cocoons of 21.34%, 12.94%, 11.2%, respectively in race C-301 and 18.49%, 15%, 15.26%, respectively in race BS-09. Meanwhile, cocoon defect types in race C-301 and BS-09 were outer defects consisting of printed, outside stained, malformed, very small, double cocoons, and inner defect consist of thin-end and inside stained cocoons. As a whole, acid rain treatments to defective cocoon of Bombyx mori L. in C-301 and BS-09 races showed no significant effect to defective cocoons.

Varying stiffness and load distributions in defective ball bearings: Analytical formulation and application to defect size estimation

This paper presents an analytical formulation of the load distribution and varying effective stiffness of a ball bearing assembly with a raceway defect of varying size, subjected to static loading in the radial, axial and rotational degrees of freedom. The analytical formulation is used to study the effect of the size of the defect on the load distribution and varying stiffness of the bearing assembly. The study considers a square-shaped outer raceway defect centered in the load zone and the bearing is loaded in the radial and axial directions while the moment loads are zero. Analysis of the load distributions shows that as the defect size increases, defect-free raceway sections are subjected to increased static loading when one or more balls completely or partly destress when positioned in the defect zone. The stiffness variations that occur when balls pass through the defect zone are significantly larger and change more rapidly at the defect entrance and exit than the stiffness variations that occur for the defect-free bearing case. These larger, more rapid stiffness variations generate parametric excitations which produce the low frequency defect entrance and exit events typically observed in the vibration response of a bearing with a square-shaped raceway defect. Analysis of the stiffness variations further shows that as the defect size increases, the mean radial stiffness decreases in the loaded radial and axial directions and increases in the unloaded radial direction. The effects of such stiffness changes on the low frequency entrance and exit events in the vibration response are simulated with a multi-body nonlinear dynamic model. Previous work used the time difference between the low frequency entrance event and the high frequency exit event to estimate the size of the defect. However, these previous defect size estimation techniques cannot distinguish between defects that differ in size by an integer number of the ball angular spacing, and a third feature of the vibration response is therefore required to distinguish between such defects. It is hypothesized and validated through simulations that when the static load remains constant, the third distinguishing feature is the characteristic frequencies of the low frequency event.

Evaluation of Electromagnetic Inspection of Outer Side Defect on Small Diameter and Thick Steel Tube With Steel Support Using 3-D Nonlinear FEM

Steel tubes are used in the heat exchanger in the petrochemical plant. Since these steel tubes are grouped in a bundle by the support steel plate, it is necessary to inspect the existence of defects from the inside of each tube. In these steel tubes, the corrosion or the defects are generated by the friction with the support steel plate at the outer side of steel tube. In this paper, the electromagnetic inspection method using only ac magnetic field is proposed. The behavior of ac flux in the steel tube and support steel plate is examined using 3-D nonlinear finite element method taking account of eddy current. It is shown that the detection of outer side defect is possible without being influenced by the support steel plate with high permeability. The usefulness of this proposal inspection method is shown by verification experiment.

Investigation of passivation and galvanic corrosion of Ti–Nb alloys and pure titanium

The aim of this study was to investigate the role of the passive layers in galvanic corrosion of Ti–Nb alloys and commercially pure titanium (cp‐Ti). Ti–Nb alloys with 5, 10, 15, and 20 wt% niobium (Nb) content were prepared using an arc‐melting technique under high purity Ar gas. The cp‐Ti was used as a control. The electrochemical corrosion behaviors were investigated by A.C. impedance, potentiodynamic polarization, and galvanic corrosion tests. According to the results of impedance analysis, the passivation layer on Ti–Nb alloys consisted of outer, intermediate, inner, and metal defect layers, while the passivation layer on cp‐Ti consisted of outer, intermediate, and inner layers. According to the results of anodic polarization tests, Ti–Nb alloys exhibited better zero potentials and reduced zero current densities. The outer layer and the inner layer of Ti–Nb alloys and cp‐Ti had an effect mainly on the values of the initial galvanic current density and the sign of galvanic current density, respectively. Ti–10Nb alloy exhibited a relatively high initial galvanic current density compared to the other Ti–Nb alloys. Unlike Ti–5Nb, Ti–10Nb, and Ti–15Nb, which exhibited galvanic current densities with a minus sign, Ti–20Nb exhibited a galvanic current density with a plus sign due to its weaker inner layer than that of Ti.

Analyses of contact forces and vibration response for a defective rolling element bearing using an explicit dynamics finite element model

This paper provides insights into the physical mechanism by which defect-related impulsive forces, and consequently, vibrations are generated in defective rolling element bearings. A dynamic nonlinear finite element model of a rolling element bearing with an outer raceway defect was numerically solved using the explicit dynamics finite element software package, LS-DYNA. A hypothesis was developed to explain the numerical noise observed in the predicted vibrations and contact forces, and the noise frequencies were analytically estimated. In-depth analyses of the numerically estimated dynamic contact forces between the rolling elements and the raceways of a bearing, which are not measured in practice, and have not been reported previously, are presented in this paper. Several events associated with the traverse of the rolling elements through the outer raceway defect are elaborated, and the impulsive force generating mechanism is explained. It was found that the re-stressing of the rolling elements that occurs near the end of a raceway defect generates a burst of multiple short-duration force impulses. The modelling results also highlight that much higher contact forces and accelerations are generated on the exit of the rolling elements out of defect compared to when they strike the defective surface. A bearing with a machined outer raceway defect was tested in a controlled experiment; the measured acceleration response compared favourably with the numerically modelled acceleration results, thereby, validating the low- and high-frequency characteristics of the de-stressing and re-stressing of the rolling elements, respectively.

Vibration Analysis of Rolling Element Bearings Defects

In this work, vibration analysis of rolling element bearings (REBs) defects is studied. The REBs are the most widely used mechanical parts in rotating machinery under high load and high rotational speeds. When the defect in a rolling element comes into contact with another element surface, an impact force is generated which is resulting in an impulsive response of the bearing. A defect at any element of the REB transmits to all other elements such as outer race, inner race, ball and, train cage of the bearing. The defect in rolling elements may lead to serious catastrophic consequences resulting in costly downtime. For this purpose, the vibration analysis technique which is a reliable and accurately detecting defect in the bearing elements is used. The vibration data captured and used for determination and validation is composed from four different defects states of the REB -outer raceway defect, inner raceway defect, ball defect, and combination of the bearing elements defect- and one representing normal state of the bearing for four different running speeds with two load levels. The results obtained from the experiments have illustrated and explained.

Role of ganglion cell complex in visual recovery following surgical internal limiting membrane peeling.

To investigate the Ganglion Cell Complex (GCC) thickness change and visual recovery correlation after surgery for an idiopathic epiretinal membrane (ERM). In this prospective, observational, case control study 30 eyes underwent vitrectomy for idiopathic ERM. We analysed best-corrected visual acuity (BCVA), mean macular thickness and mean GCC thickness one day before surgery, seven days and six months after surgery. Internal segment/outer segment junction, external limiting membrane, cone outer segment tips defects and intraretinalfluid were also investigated throughout the follow-up. Baseline GCC thickness was higher in patients with ERM (130 ± 13 μm) compared with healthy eyes (94 ± 5 μm; p < 0.0001). GCC thickness decreased after surgery to 89 ± 11 μm (p < 0.0001), reaching a value similar to controls (p = 0.12). Preoperative macular thickness was 318 ± 32 μm and decreased to 281 ± 18 μm (p < 0.0001), remaining significantly higher than controls (260 ± 8 μm; p < 0.0001). The GCC proportion of the whole macular thickness was also reduced six months after surgery (p < 0.0001). Post-operative BCVA gain showed direct correlation with GCC reduction (R = 0.67, p < 0.0001), but did not correlate with the mean macular thickness reduction (R < 0.01, p = 0.97). Ganglion cell complex thickness is higher in eyes with idiopathic ERM, and after surgery turns back to similar values of healthy eyes. Post-operative GCC reduction is proportionally higher than thinning of the whole retina, and this reduction is correlated with visual restoration.

Analysis of bearing stiffness variations, contact forces and vibrations in radially loaded double row rolling element bearings with raceway defects

A method is presented for calculating and analyzing the quasi-static load distribution and varying stiffness of a radially loaded double row bearing with a raceway defect of varying depth, length, and surface roughness. The method is applied to ball bearings on gearbox and fan test rigs seeded with line or extended outer raceway defects. When balls pass through the defect and lose all or part of their load carrying capacity, the load is redistributed between the loaded balls. This includes balls positioned outside the defect such that good raceway sections are subjected to increased loading when a defect is present. The defective bearing stiffness varies periodically at the ball spacing, and only differs from the good bearing case when balls are positioned in the defect. In this instance, the stiffness decreases in the loaded direction and increases in the unloaded direction. For an extended spall, which always has one or more balls positioned in the defect, this results in an average stiffness over the ball spacing period that is lower in the loaded direction in comparison to both the line spall and good bearing cases. The variation in bearing stiffness due to the defect produces parametric excitations of the bearing assembly. The qualitative character of the vibration response correlates to the character of the stiffness variations. Rapid stiffness changes at a defect exit produce impulses. Slower stiffness variations due to large wavelength waviness features in an extended spall produce low frequency excitation which results in defect components in the velocity spectra. The contact forces fluctuate around the quasi-static loads on the balls, with rapid stiffness changes producing high magnitude impulsive force fluctuations. Furthermore, it is shown that analyzing the properties of the dynamic model linearized at the quasi-static solutions provides greater insight into the time–frequency characteristics of the vibration response. This is demonstrated by relating the low frequency event that occurs when a ball enters a line spall to the dynamic properties of the bearing assembly.

Correlation Between Spectral-Domain OCT Findings and Visual Acuity in X-Linked Retinoschisis

To investigate the tomographic characteristics of the outer retina and choroid and their relationship with visual acuity in X-linked juvenile retinoschisis (XLRS) patients using spectral-domain optical coherence tomography (SD-OCT). In this retrospective, observational, case-control study, we analyzed 20 eyes of 10 patients with XLRS using SD-OCT. The clinical and tomographic features of the outer retina, including the external limiting membrane (ELM), inner segment/outer segment (IS/OS) junction, cone cell outer segment tips (COST) line, photoreceptor outer segment (PROS) length, and choroid, were evaluated. As controls, 40 age-, sex-, and refraction-matched healthy eyes (1:2 matched) were randomly selected and imaged in parallel. The most prevalent area of abnormality in the outer retina layer of our patients was the outer plexiform layer (OPL; 60% of all affected eyes) and COST line (75% of all affected eyes). On average, the subfoveal choroid and PROS lengths were 35 μm thicker and 19 μm thinner, respectively, in XLRS patients (P = 0.084 and P < 0.001, respectively). A dominant IS/OS junction, COST line defects, and PROS length were related to patient best-corrected visual acuity (BCVA; P = 0.029, P = 0.001, and P < 0.001, respectively) by univariate analysis. Cone cell outer segment tips line defect and PROS length were the only factors related to BCVA in multivariate analysis (P = 0.028 and 0.003, respectively). Outer plexiform layer and photoreceptor microstructure defects are frequent in XLRS patients. Cone cell outer segment tips line defects and shortened PROS lengths as well as other photoreceptor microstructure defects may be closely related to poor vision in XLRS.

Structure and function of the beta‐barrel assembly machine and its chaperones (224.2)

Transmembrane proteins in the bacterial outer membrane display a characteristic beta‐barrel architecture. Folding and insertion of these Outer Membrane Proteins (OMPs) is essential for Gram‐Negative bacteria and requires the action of both periplasmic chaperones and the outer membrane complex known as beta‐Barrel Assembly Machine (BAM). The BAM complex is composed of BamA, a bετα‐barrel OMP itself; and four associated lipoproteins: BamB, C, D and E. BamA and BamD are essential for viability and appear to be present in all bacteria with an outer membrane. Whereas the phylogenetic distribution of BamB, C and E is not well defined, these lipoproteins are also important for OMP biogenesis and their deletion in E. coli results in outer membrane permeability defects. I present the crystal and NMR structures of BAM subunits as well as a complex between BamB and a periplasmic fragment of BamA, which begin to illuminate the architecture of this essential molecular machine. We show that chaperones prevent nascent OMP aggregation in the periplasm and maintain them in an unfolded state. The central BAM component, BamA, undergoes conformational transitions that are essential for its role in OMP folding and insertion, whereas BamB is proposed to modulate these conformational changes.

Structure and Function of the Beta-Barrel Assembly Machine and its Associated Chaperones

Membrane insertion of βeτα-barrel Outer Membrane Proteins (OMPs) is essential for Gram-Negative bacteria and requires the action of both periplasmic chaperones and the outer membrane complex known as beta-Barrel Assembly Machinery (BAM). Interfering with OMP transport and assembly may be an effective strategy for antibiotic development; much like β-lactams are effective by inhibiting cell wall synthesis. Therefore, it is crucial to understand the mechanisms by which periplasmic chaperones and the BAM complex work together to control OMP transport and assembly. The BAM complex is composed of BamA, a β-barrel OMP itself; and four associated lipoproteins: BamB, C, D and E. BamA and BamD are essential for viability and appear to be present in all bacteria with an outer membrane. Whereas the phylogenetic distribution of BamB, C and E is not well defined, these lipoproteins are also important for OMP biogenesis and their deletion in E. coli results in outer membrane permeability defects. In the current model, periplasmic chaperones prevent OMP aggregation in the periplasm and deliver their cargo to the BAM complex for insertion into the outer membrane. However, the molecular mechanisms mediating this process are still obscure. I present the crystal and NMR structures of BamB, BamD and BamC as well as the periplasmic domain of BamA. In addition we have just solved the structure of a complex between BamB and the periplasmic fragment of BamA, which begins to illuminate the architecture of this essential molecular machine. Using complementary biochemical and genetic experiments we show that the periplasmic domain of BamA is undergoes conformational transitions that are essential for its role in OMP folding and insertion. I'll present the implications of these structure/function studies for the mechanism of OMP folding and insertion.

Honeycomb photonic crystal vertical-cavity surface-emitting lasers: coupled cavities enhancing the single-mode range

A new design is proposed to increase the single-mode current range of low threshold current, photonic crystal vertical-cavity surface-emitting lasers. Our method is based on the optical coupling between the usual central defect and six others of nearly identical sizes. The resulting honeycomb configuration aims to spread higher supermodes in transverse directions, and to reduce their overlap with a central current-injected region. Simultaneous confinement of the fundamental mode within the central cavity and the shift of higher modes toward outer trapping defects can lead to stable single-mode operation. Simulations confirm that either in-phase or out-of-phase coupled supermodes could be promoted by slightly modifying the areas of outer cavities, while thermal lensing always stabilizes the in-phase coupled supermodes. The single-mode current regime should be extended noticeably compared to the conventional single-defect lasers.

Response to Fajgenbaum

Sir, We thank Dr Fajgenbaum1 for his interest in our recent case series of maculopathy in poppers users2 and for debate on this matter with respect to photic maculopathy. The similarity of clinical signs in ‘poppers maculopathy' patients with those described in some patients with photic maculopathy is intriguing and as was also demonstrated in Dr Fajgenbaum's case report. We doubt the suggestion that poppers inhalation could lead to hallucinations or drastically altered consciousness, resulting in entrancement with bright lights or the sun. The psychogenic effects of poppers are well documented, but do not, in our opinion, lead to this sort of behaviour. It is also recognised that poppers use can be linked to abuse of other compounds, which may have more potent hallucinogenic effects. We also agree that as poppers are sometimes used in raves where exposure to unsafe use of laser lights is a potential risk, these matters need to be considered in the differential diagnosis of individuals with acquired foveal defects. To answer the question about substance abuse and exposure to light in our cases, a detailed drug and social history was taken. Cases were questioned about prolonged solar or other lights gazing and which was denied in all cases. As we stated there were several features of our cases that support on the balance of probabilities evidence of causality of poppers maculopathy as based on the Bradford-Hill criteria. Mainster et al3 has provided helpful advice on assessment of alleged retinal laser injury patients and which can also in our opinion be extrapolated to alleged photic retinal injury. Furthermore, it is now increasingly recognised that the signs of alleged solar maculopathy on SD-OCT imaging are varied. As discussed in our paper, it is not possible to prove causality of poppers maculopathy and we agree that differential diagnosis of outer lamellar defects can be challenging4 and that a detailed history should be taken.

Paracentral Acute Middle Maculopathy

With the advent of more sophisticated imaging systems, such as spectral domain optical coherence tomography (SD-OCT), disruption of the inner segment/outer segment (IS/OS) band, and thinning of the outer nuclear layer (ONL) have been identified in association with acute macular neuroretinopathy (AMN). To characterize a new SD-OCT presentation of AMN as a paracentral acute middle maculopathy and to describe multimodal imaging findings that implicate an underlying pathogenesis related to retinal capillary ischemia. Retrospective observational case series (January 1, 2012, to January 1, 2013) reviewing clinical and imaging data from 9 patients (11 eyes) with AMN at 6 tertiary referral centers. Lesions were classified as type 1 or 2 in relation to the SD-OCT location of the lesion above (type 1) or below (type 2) the outer plexiform layer (OPL) at 6 tertiary referral centers. Of the 9 patients, 5 were female and 4 were male (mean age, 47.6 years; range, 21-65 years). All patients presented with an acute paracentral scotoma and demonstrated a classic dark gray paracentral lesion with near-infrared imaging. Visual acuity ranged from 20/15 to 20/30. Six eyes (5 patients) had type 1 SD-OCT lesions, also referred to as paracentral acute middle maculopathy, and 5 eyes (4 patients) had type 2 SD-OCT lesions. Although type 1 lesions lead to inner nuclear layer (INL) thinning, type 2 lesions resulted in ONL thinning. Type 2 lesions were always associated with significant outer macular defects, including disruption of the inner segment/outer segment and outer segment/retinal pigment epithelium bands, whereas type 1 lesions spared the outer macula. Paracentral acute middle maculopathy may represent a novel variant of AMN that affects the middle layers of the macula above the OPL as diagnosed with SD-OCT imaging. Two types of AMN lesions may be seen with SD-OCT occurring above and below the OPL. Type 1 refers to hyperreflective bands in the OPL/INL region with subsequent INL thinning. Type 2 is hyperreflective bands in the OPL/ONL region with subsequent ONL thinning. Type 2 lesions may be associated with concomitant defects of the inner segment/outer segment layer. We propose that each of these lesions may be explained by occlusion of either the superficial capillary plexus (type 1) or deep capillary plexus (type 2) located in the innermost and outermost portion of the INL, respectively, immediately adjacent to each corresponding lesion type.

Acoustic emission-based early fault detection in tapered roller bearings

This paper proposes an acoustic emissions-based method for monitoring tapered roller bearings. This method monitors tracking time-based fault indicators (i.e. RMS, peak value, ring-down count and kurtosis) obtained using the AE signal. Experiments were carried out on a dedicated test bench for different levels of tapered roller bearing outer and inner race defect severity. Although the fault indicators studied could not discriminate between outer and inner raceway defects, the experimental results highlighted the proposed indicators' tapered roller bearing fault detection and fault severity assessment ability (i.e. peak value, RMS and ring-down count).

Persistent outer retinal fluid following non-posturing surgery for idiopathic macular hole

AimTo present the anatomical and visual outcomes of patients with hypo-reflective cystic defects in outer fovea (outer foveal defect; OFD) in macular holes repaired with non-posturing vitrectomy and short term...

Successful treatment of an overlapping choriocapillaritis between multifocal choroiditis and acute zonal occult outer retinopathy (AZOOR) with adalimumab (Humira™)

To report a case of overlapping choriocapillaritis that initially presented as multifocal choroiditis (MFC) but later showed features compatible with acute zonal occult outer retinopathy (AZOOR) resistant to standard immunosuppression that responded only to adalimumad therapy. A 41-year-old patient presented with multiple small, discrete yellow-whitish spots in both eyes, compatible with MFC. A few weeks later, despite treatment with sub-Tenon and systemic corticosteroids, a choroidal neovascularization occurred in the right eye. The patient was treated with intravitreal anti-vascular endothelial growth factor. After 2 months, reduced visual acuity, photopsia and visual field defect in the left eye occurred. Spectral domain optical coherence tomography revealed photoreceptor outer segment defects common to all choriocapillaritis. The additional finding of an annular scotoma and a 360° ring on indocyanine green angiography led us to make the diagnosis of presumed AZOOR. Despite the combination of several immunosuppressive agents leading to temporary control of the disease, the patient experienced a further worsening. At that point, adalimumab was introduced, which led to an obvious improvement. This case supports the hypothesis that two different entities of the so-called AZOOR complex can be possible in the same eye, even asynchronously. In our case, anti-tumor necrosis factor alpha monoclonal antibody therapy represented a valid treatment option in a patient unresponsive to traditional immunosuppressive treatments.

The biology of hair diversity

Hair diversity, its style, colour, shape and growth pattern is one of our most defining characteristics. The natural versus temporary style is influenced by what happens to our hair during our lifetime, such as genetic hair loss, sudden hair shedding, greying and pathological hair loss in the various forms of alopecia because of genetics, illness or medication. Despite the size and global value of the hair care market, our knowledge of what controls the innate and within-lifetime characteristics of hair diversity remains poorly understood. In the last decade, drivers of knowledge have moved into the arena of genetics where hair traits are obvious and measurable and genetic polymorphisms are being found that raise valuable questions about the biology of hair growth. The recent discovery that the gene for trichohyalin contributes to hair shape comes as no surprise to the hair biologists who have believed for 100years that hair shape is linked to the structure and function of the inner root sheath. Further conundrums awaiting elucidation include the polymorphisms in the androgen receptor (AR) described in male pattern alopecia whose location on the X chromosome places this genetic contributor into the female line. The genetics of female hair loss is less clear with polymorphisms in the AR not associated with female pattern hair loss. Lifestyle choices are also implicated in hair diversity. Greying, which also has a strong genetic component, is often suggested to have a lifestyle (stress) influence and hair follicle melanocytes show declining antioxidant protection with age and lowered resistance to stress. It is likely that hair research will undergo a renaissance on the back of the rising information from genetic studies as well as the latest contributions from the field of epigenetics.